diff --git a/components/buildintf/packagedependencyintf.pas b/components/buildintf/packagedependencyintf.pas
index d76ca5458d..9162d6b7f2 100644
--- a/components/buildintf/packagedependencyintf.pas
+++ b/components/buildintf/packagedependencyintf.pas
@@ -121,7 +121,7 @@ var
   PkgName: String;
 begin
   Result:=false;
-  if CompareFileExt(AFilename,'lpk',true)<>0 then exit;
+  if not FilenameExtIs(AFilename,'lpk',true) then exit;
   PkgName:=ExtractFileNameOnly(AFilename);
   if (PkgName='') or (not IsValidPkgName(PkgName)) then exit;
   Result:=true;
diff --git a/components/codetools/codetoolmanager.pas b/components/codetools/codetoolmanager.pas
index e97a4c7667..cbef3c201d 100644
--- a/components/codetools/codetoolmanager.pas
+++ b/components/codetools/codetoolmanager.pas
@@ -5873,9 +5873,9 @@ end;
 function TCodeToolManager.DoOnGetSrcPathForCompiledUnit(Sender: TObject;
   const AFilename: string): string;
 begin
-  if CompareFileExt(AFilename,'ppu',true)=0 then
+  if FilenameExtIs(AFilename,'ppu',true) then
     Result:=GetPPUSrcPathForDirectory(ExtractFilePath(AFilename))
-  else if CompareFileExt(AFilename,'dcu')=0 then
+  else if FilenameExtIs(AFilename,'dcu') then
     Result:=GetDCUSrcPathForDirectory(ExtractFilePath(AFilename))
   else
     Result:='';
diff --git a/components/codetools/definetemplates.pas b/components/codetools/definetemplates.pas
index 537b1e1111..38d52a4def 100644
--- a/components/codetools/definetemplates.pas
+++ b/components/codetools/definetemplates.pas
@@ -1939,10 +1939,7 @@ var
   FileCount: Integer;
   Abort: boolean;
   FileInfo: TSearchRec;
-  ShortFilename: String;
-  Filename: String;
-  Ext: String;
-  File_Name: String;
+  ShortFilename, Filename, File_Name: String;
 begin
   // units sources
   Units:=TStringToStringTree.Create(false);
@@ -1965,11 +1962,11 @@ begin
             continue;
           //debugln(['GatherUnitsInSearchPaths ShortFilename=',ShortFilename,' IsDir=',(FileInfo.Attr and faDirectory)>0]);
           Filename:=Directory+ShortFilename;
-          Ext:=LowerCase(ExtractFileExt(ShortFilename));
-          if (Ext='.pas') or (Ext='.pp') or (Ext='.p') or (Ext='.ppu') then begin
+          if FilenameExtIn(ShortFilename,['.pas','.pp','.p','.ppu']) then begin
             File_Name:=ExtractFileNameOnly(Filename);
             if (not Units.Contains(File_Name))
-            or ((Ext<>'.ppu') and (CompareFileExt(Units[File_Name],'ppu',true)=0))
+            or (not FilenameExtIs(ShortFilename,'.ppu',true)
+              and FilenameExtIs(Units[File_Name],'ppu',true) )
             then
               Units[File_Name]:=Filename;
           end;
@@ -1997,8 +1994,7 @@ begin
             continue;
           //debugln(['GatherUnitsInSearchPaths ShortFilename=',ShortFilename,' IsDir=',(FileInfo.Attr and faDirectory)>0]);
           Filename:=Directory+ShortFilename;
-          Ext:=LowerCase(ExtractFileExt(ShortFilename));
-          if (Ext='.inc') then begin
+          if FilenameExtIs(ShortFilename,'.inc') then begin
             File_Name:=ExtractFileName(Filename);
             if (not Includes.Contains(File_Name))
             then
@@ -2052,7 +2048,7 @@ begin
     //if Pos('lazmkunit',Filename)>0 then
       //debugln(['GatherUnitsInFPMSources ===== ',Filename]);
     AVLNode:=Units.Tree.FindSuccessor(AVLNode);
-    if CompareFileExt(Filename,'ppu',true)<>0 then continue;
+    if not FilenameExtIs(Filename,'ppu',true) then continue;
     // check if filename has the form
     //                  /something/units/<FPCTarget>/<pkgname>/<unitname>.ppu
     // and if there is  /something/fpmkinst/<FPCTarget>/<pkgname>.fpm
@@ -2877,7 +2873,7 @@ begin
     Item:=PStringToStringItem(Node.Data);
     Unit_Name:=Item^.Name;
     Filename:=Item^.Value;
-    if CompareFileExt(Filename,'ppu',true)=0 then begin
+    if FilenameExtIs(Filename,'ppu',true) then begin
       SrcFilename:=UnitToSource[Unit_Name];
       if SrcFilename<>'' then begin
         DuplicateFilenames:=UnitToDuplicates[Unit_Name];
@@ -3945,7 +3941,7 @@ begin
 
   // dcc*.exe
   if LazStartsText('dcc',ShortFilename)
-  and ((ExeExt='') or (CompareFileExt(Filename,ExeExt)=0))
+  and ( (ExeExt='') or FilenameExtIs(Filename,ExeExt) )
   then
     exit(pcDelphi);
 
@@ -3980,7 +3976,7 @@ begin
 
   // dcc*.exe
   if (CompareFilenames(LeftStr(ShortFilename,3),'dcc')=0)
-      and ((ExeExt='') or (CompareFileExt(AFilename,ExeExt)=0))
+  and ( (ExeExt='') or FilenameExtIs(AFilename,ExeExt) )
   then begin
     Kind:=pcDelphi;
     exit(true);
@@ -4048,7 +4044,7 @@ begin
 
   // allow ppcxxx.exe
   if (LazStartsText('ppc',ShortFilename))
-  and ((ExeExt='') or (CompareFileExt(AFilename,ExeExt)=0))
+  and ( (ExeExt='') or FilenameExtIs(AFilename,ExeExt) )
   then
     exit(true);
 
@@ -9111,7 +9107,7 @@ begin
       end;
       // check if the system ppu exists
       HasPPUs:=(Kind=pcFPC) and (Units<>nil)
-          and (CompareFileExt(Units['system'],'ppu',true)=0);
+          and FilenameExtIs(Units['system'],'ppu',true);
       // check compiler version define
       if (CTConsoleVerbosity>=-1) and (Defines<>nil) then begin
         case Kind of
@@ -10417,7 +10413,7 @@ begin
   if (ConfigCache.Units<>nil) then begin
     UnitInFPCPath:=ConfigCache.Units[AnUnitName];
     //if Pos('lazmkunit',AnUnitName)>0 then debugln(['TFPCUnitSetCache.GetUnitSrcFile UnitInFPCPath=',UnitInFPCPath]);
-    if (CompareFileExt(UnitInFPCPath,'ppu',true)=0) then begin
+    if FilenameExtIs(UnitInFPCPath,'ppu',true) then begin
       // there is a ppu
     end else if UnitInFPCPath<>'' then begin
       // there is a pp or pas in the FPC search path
@@ -10469,7 +10465,7 @@ begin
   if ConfigCache.Units=nil then exit;
   Result:=ConfigCache.Units[AUnitName];
   if Result='' then exit;
-  if CompareFileExt(Result,'ppu',true)<>0 then
+  if not FilenameExtIs(Result,'ppu',true) then
     Result:='';
 end;
 
diff --git a/components/codetools/directorycacher.pas b/components/codetools/directorycacher.pas
index 027573c79a..bb4841143e 100644
--- a/components/codetools/directorycacher.pas
+++ b/components/codetools/directorycacher.pas
@@ -452,7 +452,7 @@ begin
           end;
           // try also different extensions
           for pe:=Low(TCTPascalExtType) to High(TCTPascalExtType) do begin
-            if CompareFileExtQuick(Filename,CTPascalExtension[pe])<>0 then
+            if not FilenameExtIs(Filename,CTPascalExtension[pe]) then
             begin
               AliasFilename:=ChangeFileExt(Filename,'.pas');
               if FileExistsCached(AliasFilename) then begin
@@ -869,7 +869,7 @@ begin
     end;
     // try different extensions too
     for pe:=Low(TCTPascalExtType) to High(TCTPascalExtType) do begin
-      if CompareFileExtQuick(Result,CTPascalExtension[pe])<>0 then
+      if not FilenameExtIs(Result,CTPascalExtension[pe]) then
       begin
         AliasFilename:=ChangeFileExt(Result,CTPascalExtension[pe]);
         if FileExistsCached(AliasFilename) then begin
diff --git a/components/codetools/ppugraph.pas b/components/codetools/ppugraph.pas
index c0867946e4..02fc34f169 100644
--- a/components/codetools/ppugraph.pas
+++ b/components/codetools/ppugraph.pas
@@ -697,7 +697,7 @@ begin
       if (FileInfo.Name='.') or (FileInfo.Name='..') or (FileInfo.Name='') then
         continue;
       Filename:=FileInfo.Name;
-      if (CompareFileExt(Filename,'ppu',true)<>0) then continue;
+      if not FilenameExtIs(Filename,'ppu',true) then continue;
       AUnitName:=ExtractFileNameOnly(Filename);
       Filename:=AppendPathDelim(Directory)+Filename;
       if not LazIsValidIdent(AUnitName,true,true) then begin
diff --git a/components/datadict/frmbaseconfigcodegenerator.pp b/components/datadict/frmbaseconfigcodegenerator.pp
index 1e343d66e6..80887835a8 100644
--- a/components/datadict/frmbaseconfigcodegenerator.pp
+++ b/components/datadict/frmbaseconfigcodegenerator.pp
@@ -5,9 +5,11 @@ unit frmBaseConfigCodeGenerator;
 interface
 
 uses
-  Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls,
-  StdCtrls, EditBtn, ComCtrls, RTTIGrids, CheckLst, fpddcodegen, Buttons,
-  ActnList, ButtonPanel, ldd_consts, SynEdit, SynHighlighterPas;
+  Classes, SysUtils, fpddcodegen,
+  Forms, Controls, Graphics, Dialogs, ExtCtrls, StdCtrls, EditBtn, ComCtrls,
+  RTTIGrids, CheckLst, Buttons, ActnList, ButtonPanel,
+  LazFileUtils,
+  ldd_consts, SynEdit, SynHighlighterPas;
 
 type
 
@@ -246,7 +248,7 @@ begin
      NewName:=ExtractFileName(FEFile.FileName);
      FLastName:=NewName;
      // Strip off known extensions
-     if (IndexStr(LowerCase(ExtractFileExt(NewName)),['.pas','.pp','.inc','.lpr','.dpr'])<>-1) then
+     if FilenameExtIn(NewName,['.pas','.pp','.inc','.lpr','.dpr']) then
        FCodeOptions.UnitName:=ChangeFileExt(NewName,'')
      else
        FCodeOptions.UnitName:=NewName;
diff --git a/components/favorites/favorites_impl.pas b/components/favorites/favorites_impl.pas
index 0bfefdff6b..d4c3ba345d 100644
--- a/components/favorites/favorites_impl.pas
+++ b/components/favorites/favorites_impl.pas
@@ -165,7 +165,7 @@ end;
 procedure TOpenFileFavToolButton.RefreshMenu(Sender: TObject);
 var
   xM, xSep: TMenuItem;
-  xFavoriteFile, xExt: string;
+  xFavoriteFile: string;
   xMI, xAddToFav: TFileNameMenuItem;
   xProj: TLazProject;
   xMIndex: Integer;
@@ -182,8 +182,7 @@ begin
     xMI.FileName := xFavoriteFile;
     xMI.Caption := xFavoriteFile;
     xMI.OnClick := @mnuFavoriteFile;
-    xExt := ExtractFileExt(xFavoriteFile);
-    if SameFileName(xExt, '.lpi') or SameFileName(xExt, '.lpr') then
+    if FilenameExtIn(xFavoriteFile,['.lpi','.lpr']) then
       xMI.ImageIndex := LoadProjectIconIntoImages(xFavoriteFile, DropdownMenu.Images, FIndex);
 
     xM.Insert(xMIndex, xMI);
diff --git a/components/fpdebug/fpimgreadermacho.pas b/components/fpdebug/fpimgreadermacho.pas
index d3b057a644..dac216fed8 100644
--- a/components/fpdebug/fpimgreadermacho.pas
+++ b/components/fpdebug/fpimgreadermacho.pas
@@ -6,7 +6,7 @@ interface
 
 uses
   Classes, SysUtils, contnrs,
-  LazFglHash, LazLoggerBase, LazUTF8,
+  LazFglHash, LazLoggerBase, LazFileUtils, LazUTF8,
   DbgIntfBaseTypes,
   // FpDebug
   macho, FpImgReaderMachoFile, FpImgReaderBase, fpDbgSymTable, FpDbgUtil;
@@ -365,7 +365,7 @@ begin
   dSYMFilename:=ChangeFileExt(PLoader.FileName, '.dSYM');
   dSYMFilename:=dSYMFilename+'/Contents/Resources/DWARF/'+ExtractFileName(fname); // TDbgProcess.Name
 
-  if ExtractFileExt(dSYMFilename)='.app' then
+  if FilenameExtIs(dSYMFilename,'.app',true) then
     dSYMFilename := ChangeFileExt(dSYMFilename,'');
 
   if FileExists(dSYMFilename) then
diff --git a/components/fpvectorial/htmlvectorialreader.pas b/components/fpvectorial/htmlvectorialreader.pas
index e613e9945b..ccc76cb236 100644
--- a/components/fpvectorial/htmlvectorialreader.pas
+++ b/components/fpvectorial/htmlvectorialreader.pas
@@ -620,15 +620,8 @@ begin
 end;
 
 class function TvHTMLVectorialReader.IsSupportedRasterImage(AFileName: string): Boolean;
-var
-  lExt: string;
 begin
-  Result := False;
-  lExt := LowerCase(ExtractFileExt(AFileName));
-  case lExt of
-  '.png', '.jpg', '.jpeg', '.bmp', '.xpm', '.gif':
-    Result := True
-  end;
+  Result := FilenameExtIn(AFileName,['.png','.jpg','.jpeg','.bmp','.xpm','.gif']);
 end;
 
 initialization
diff --git a/components/fpweb/fpwebnewhtmlfileunit.pas b/components/fpweb/fpwebnewhtmlfileunit.pas
index 253176bc3e..6b53b0430c 100644
--- a/components/fpweb/fpwebnewhtmlfileunit.pas
+++ b/components/fpweb/fpwebnewhtmlfileunit.pas
@@ -34,8 +34,12 @@ unit fpWebNewHTMLFileUnit;
 interface
 
 uses
-  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ButtonPanel,
-  StdCtrls, ComCtrls;
+  Classes, SysUtils,
+  Forms, Controls, Graphics, Dialogs, ButtonPanel, StdCtrls, ComCtrls,
+  FileUtil, LazFileUtils,
+  ProjectIntf, LazIDEIntf,
+  fpWebStrConsts;
+
 
 type
 
@@ -79,8 +83,6 @@ const
 
 implementation
 
-uses fpWebStrConsts, SrcEditorIntf, ProjectIntf, LazIDEIntf;
-
 {$R *.lfm}
 const
   HTMLHeaders : array [0..7] of string =
@@ -143,18 +145,17 @@ end;
 procedure TfpWebNewHTMLFileForm.FillLinks;
 var
   i:integer;
-  S, Ext: string;
+  S: string;
 begin
   if Assigned(LazarusIDE) and Assigned(LazarusIDE.ActiveProject) then
   begin
     for i:=0 to LazarusIDE.ActiveProject.FileCount - 1 do
     begin
       S:=LazarusIDE.ActiveProject.Files[i].Filename;
-      Ext:=ExtractFileExt(S);
-      if CompareText(Ext, '.JS') = 0 then
+      if FilenameExtIs(S, '.JS') then
         edtJS.Items.Add(S)
       else
-      if CompareText(Ext, '.CSS') = 0 then
+      if FilenameExtIs(S, '.CSS') then
         edtCSS.Items.Add(S);
     end;
   end;
diff --git a/components/fpweb/weblazideintf.pp b/components/fpweb/weblazideintf.pp
index 72475f1f91..1d8a7d366e 100644
--- a/components/fpweb/weblazideintf.pp
+++ b/components/fpweb/weblazideintf.pp
@@ -22,8 +22,7 @@ unit WebLazIDEIntf;
 interface
 
 uses
-  Classes, SysUtils, fpWeb, fpHTML, fpdatasetform,  IDEExternToolIntf,
-  Controls, Dialogs, forms, LazIDEIntf, ProjectIntf, SrcEditorIntf, IDEMsgIntf,
+  Classes, SysUtils, fpWeb, fpHTML, fpdatasetform,
   fpextjs, extjsjson, extjsxml, fpjsonrpc, jstree,jsparser,
   fpextdirect,fpwebdata,
 {$IF FPC_FULLVERSION>=30004}
@@ -35,7 +34,12 @@ uses
   fpoauth2,
   fpoauth2ini,
 {$ENDIF}
-  webjsonrpc, fpWebStrConsts;
+  webjsonrpc,
+  Controls, Dialogs, Forms,
+  LazFileUtils,
+  IDEExternToolIntf, ProjectIntf,
+  LazIDEIntf, SrcEditorIntf, IDEMsgIntf,
+  fpWebStrConsts;
 
 type
   { TCGIApplicationDescriptor }
@@ -1096,7 +1100,6 @@ function TJSSyntaxChecker.CheckSource(Sender: TObject; var Handled: boolean
 
 Var
   AE : TSourceEditorInterface;
-  E : String;
   S : TStringStream;
 
 begin
@@ -1106,9 +1109,8 @@ begin
   AE:=SourceEditorManagerIntf.ActiveEditor;
   If (AE<>Nil) then
     begin
-    E:=ExtractFileExt(AE.FileName);
     FSFN:=ExtractFileName(AE.FileName);
-    Handled:=CompareText(E,'.js')=0;
+    Handled:=FilenameExtIs(AE.FileName,'.js');
     If Handled then
       begin
       S:=TStringStream.Create(AE.SourceText);
diff --git a/components/lazutils/lazfileutils.pas b/components/lazutils/lazfileutils.pas
index 62f258ad61..716fccac87 100644
--- a/components/lazutils/lazfileutils.pas
+++ b/components/lazutils/lazfileutils.pas
@@ -31,12 +31,12 @@ function CompareFilenamesIgnoreCase(const Filename1, Filename2: string): integer
 function CompareFilenameStarts(const Filename1, Filename2: string): integer;
 function CompareFilenames(Filename1: PChar; Len1: integer;
   Filename2: PChar; Len2: integer): integer; overload;
-function CompareFilenamesP(Filename1, Filename2: PChar;
-  IgnoreCase: boolean = false // false = use default
-  ): integer;
+function CompareFilenamesP(Filename1, Filename2: PChar; IgnoreCase: boolean=false): integer;
 function CompareFileExt(const Filename: string; Ext: string; CaseSensitive: boolean): integer;
 function CompareFileExt(const Filename, Ext: string): integer;
-function CompareFileExtQuick(const Filename: string; LowerExt: string): integer;
+function FilenameExtIs(const Filename,Ext: string; CaseSensitive: boolean=false): boolean;
+function FilenameExtIn(const Filename: string; Exts: array of string;
+  CaseSensitive: boolean=false): boolean;
 
 function DirPathExists(DirectoryName: string): boolean;
 function DirectoryIsWritable(const DirectoryName: string): boolean;
@@ -318,8 +318,7 @@ begin
   {$ENDIF}
 end;
 
-function CompareFilenamesP(Filename1, Filename2: PChar;
-  IgnoreCase: boolean = false): integer;
+function CompareFilenamesP(Filename1, Filename2: PChar; IgnoreCase: boolean): integer;
 {$IFDEF darwin}
 var
   F1: CFStringRef;
@@ -398,28 +397,78 @@ begin
                 {$IFDEF CaseInsensitiveFilenames} False {$ELSE} True {$ENDIF} );
 end;
 
-function CompareFileExtQuick(const Filename: string; LowerExt: string): integer;
-// Compares case-insensitively but only with ASCII characters.
-// LowerExt must be lowercase. It can contain a point or not.
+function FilenameExtIs(const Filename, Ext: string; CaseSensitive: boolean): boolean;
+// Return True if Filename has an extension Ext.
+// Ext can contain a point or not. Case-insensitive comparison supports only ASCII.
 var
-  FnExt: String;
-  FnPos: integer;
+  FnExtLen, ExtLen: integer;
+  FnStart, FnEnd, FnP, ExtP: PChar;
 begin
   // Filename
-  FnPos := length(Filename);
-  while (FnPos>=1) and (Filename[FnPos]<>'.') do dec(FnPos);
-  if FnPos < 1 then
-    exit(1);          // no extension in filename
-  FnExt := LowerCase(Copy(Filename, FnPos+1, length(FileName))); // FnPos+1 skips point
+  FnStart := PChar(Filename);
+  FnEnd := FnStart + Length(Filename) - 1;
+  FnP := FnEnd;
+  while (FnP >= FnStart) and (FnP^ <> '.') do
+    Dec(FnP);
+  if FnP < FnStart then
+    exit(False);          // no extension in filename
+  Inc(FnP);               // Skip '.' in Filename
+  FnExtLen := 1 + FnEnd - FnP;
   // Ext
-  if (length(LowerExt) > 1) and (LowerExt[1] = '.') then
-    Delete(LowerExt, 1, 1);
+  ExtLen := Length(Ext);
+  ExtP := PChar(Ext);
+  if ExtP^ = '.' then
+  begin
+    Inc(ExtP);            // Skip '.' in Ext
+    Dec(ExtLen);
+  end;
+  if ExtLen <> FnExtLen then
+    exit(False);          // Ext has different length than Filename
   // compare extensions
-  Result := CompareStr(FnExt, LowerExt);
-  if Result < 0 then
-    Result := -1
-  else if Result > 0 then
-    Result := 1;
+  if CaseSensitive then
+    Result := StrLComp(ExtP, FnP, ExtLen) = 0
+  else
+    Result := StrLIComp(ExtP, FnP, ExtLen) = 0
+end;
+
+function FilenameExtIn(const Filename: string; Exts: array of string;
+  CaseSensitive: boolean): boolean;
+// Return True if Filename's extension is one of Exts.
+// Ext can contain a point or not. Case-insensitive comparison supports only ASCII.
+var
+  FnExtLen, ExtLen, i: integer;
+  FnStart, FnEnd, FnP, ExtP: PChar;
+begin
+  // Filename
+  FnStart := PChar(Filename);
+  FnEnd := FnStart + Length(Filename) - 1;
+  FnP := FnEnd;
+  while (FnP >= FnStart) and (FnP^ <> '.') do
+    Dec(FnP);
+  if FnP < FnStart then
+    exit(False);          // no extension in filename
+  Inc(FnP);               // Skip '.' in Filename
+  FnExtLen := 1 + FnEnd - FnP;
+  // Extensions
+  for i := low(Exts) to high(Exts) do
+  begin
+    ExtLen := Length(Exts[i]);
+    ExtP := PChar(Exts[i]);
+    if ExtP^ = '.' then
+    begin
+      Inc(ExtP);          // Skip '.' in Ext
+      Dec(ExtLen);
+    end;
+    if ExtLen <> FnExtLen then
+      continue;           // Ext has different length than Filename
+    // compare extensions
+    if CaseSensitive then
+      Result := StrLComp(ExtP, FnP, ExtLen) = 0
+    else
+      Result := StrLIComp(ExtP, FnP, ExtLen) = 0;
+    if Result then exit;
+  end;
+  Result := False;
 end;
 
 {$IFDEF darwin}
diff --git a/components/lazutils/translations.pas b/components/lazutils/translations.pas
index 20623bee62..4a6ec289b5 100644
--- a/components/lazutils/translations.pas
+++ b/components/lazutils/translations.pas
@@ -432,7 +432,7 @@ begin
   Result:=false;
   AUnitName:='';
   Language:='';
-  if CompareFileExtQuick(Filename, 'po')=0 then
+  if FilenameExtIs(Filename, 'po') then
   begin
     NameWithoutExt:=ExtractFileNameWithoutExt(Filename);
     Ext:=ExtractFileExt(NameWithoutExt);
@@ -540,9 +540,9 @@ begin
     // Update po file with lrj, rst/rsj of RSTFiles
     for i:=0 to RSTFiles.Count-1 do begin
       Filename:=RSTFiles[i];
-      ExtLrj :=    (CompareFileExtQuick(Filename,'lrj')=0);
-      if ExtLrj or (CompareFileExtQuick(Filename,'rst')=0) or
-                   (CompareFileExtQuick(Filename,'rsj')=0) then
+      ExtLrj :=    FilenameExtIs(Filename,'lrj');
+      if ExtLrj or FilenameExtIs(Filename,'rst') or
+                   FilenameExtIs(Filename,'rsj') then
         try
           //DebugLn('');
           //DebugLn(['AddFiles2Po Filename="',Filename,'"']);
@@ -552,7 +552,7 @@ begin
           if ExtLrj then
             BasePOFile.UpdateStrings(InputLines, stLrj)
           else
-            if CompareFileExtQuick(Filename,'rsj')=0 then
+            if FilenameExtIs(Filename,'rsj') then
               BasePOFile.UpdateStrings(InputLines, stRsj)
             else
               BasePOFile.UpdateStrings(InputLines, stRst);
diff --git a/components/lazutils/winlazfileutils.inc b/components/lazutils/winlazfileutils.inc
index 2194f65122..15447fe42b 100644
--- a/components/lazutils/winlazfileutils.inc
+++ b/components/lazutils/winlazfileutils.inc
@@ -272,7 +272,7 @@ var
 begin
   Result := FileName;
   {$IFnDEF WINCE}
-  if (LowerCase(ExtractFileExt(FileName)) = '.lnk') then
+  if FilenameExtIs(FileName, '.lnk') then
   begin
     if (CoCreateInstance(CLSID_ShellLink, nil, CLSCTX_INPROC_SERVER,
                          IShellLinkW, ShellLinkW) = S_OK) then
diff --git a/components/onlinepackagemanager/opkman_common.pas b/components/onlinepackagemanager/opkman_common.pas
index 639a8ccbf1..e667defd62 100644
--- a/components/onlinepackagemanager/opkman_common.pas
+++ b/components/onlinepackagemanager/opkman_common.pas
@@ -317,7 +317,7 @@ var
     begin
       try
         repeat
-          if CompareFileExtQuick(SR.Name, 'lpk') = 0 then
+          if FilenameExtIs(SR.Name, 'lpk') then
           begin
             PackageData := TPackageData.Create;
             PackageData.FName := SR.Name;
@@ -385,7 +385,7 @@ var
       for I := 0 to SLExcludedFiles.Count - 1 do
       begin
         DebugLn(['OPM IsAllowed: ExcFile=', SLExcludedFiles.Strings[I], ', AName=', AName]);
-        if CompareFileExt(AName, SLExcludedFiles.Strings[I], False) = 0 then
+        if FilenameExtIs(AName, SLExcludedFiles.Strings[I]) then
         begin
           Result := False;
           Break;
diff --git a/components/pas2js/pjsprojectoptions.pp b/components/pas2js/pjsprojectoptions.pp
index 9e2fdad1bb..694860918a 100644
--- a/components/pas2js/pjsprojectoptions.pp
+++ b/components/pas2js/pjsprojectoptions.pp
@@ -257,7 +257,7 @@ begin
     For I:=0 to PRJ.FileCount-1 do
       begin
       PF:=PRJ.Files[i];
-      if CompareFileExtQuick(PF.Filename,'html')=0 then
+      if FilenameExtIs(PF.Filename,'html') then
         begin
         L.AddObject(PF.FileName,PF);
         If PF.CustomData[PJSIsProjectHTMLFile]='1' then
diff --git a/components/projecttemplates/idetemplateproject.pp b/components/projecttemplates/idetemplateproject.pp
index 8e426e2374..521a1937c7 100644
--- a/components/projecttemplates/idetemplateproject.pp
+++ b/components/projecttemplates/idetemplateproject.pp
@@ -276,6 +276,7 @@ begin
     Name:='Template Project';
   FVariables:=TStringList.Create;
   FIgnoreExts:=TStringList.Create;
+  {$IF FPC_FULLVERSION>=30200}FIgnoreExts.UseLocale := false;{$ENDIF}
   FIgnoreExts.CommaText:='.lpr,.lps,.lfm,.lrs,.ico,.res,.lpi,.bak';
 end;
 
@@ -326,7 +327,6 @@ Var
   I : Integer;
   AFile: TLazProjectFile;
   FN : String;
-  B : Boolean;
   L : TStringList;
   
 begin
@@ -343,13 +343,12 @@ begin
     For I:=0 to FTemplate.FileCount-1 do
       begin
       FN:=FTemplate.FileNames[I];
-      B:=CompareText(ExtractFileExt(FN),'.lpr')=0;
-      If B then
+      If FilenameExtIs(FN,'lpr') then
         begin
         FN:=FProjectDirectory+FTemplate.TargetFileName(FN,FVariables);
         AFile:=AProject.CreateProjectFile(FN);
         AFile.IsPartOfProject:=true;
-        AProject.AddFile(AFile,Not B);
+        AProject.AddFile(AFile,False);
         AProject.MainFileID:=0;
         L:=TStringList.Create;
         try
@@ -373,7 +372,7 @@ Function TTemplateProjectDescriptor.CreateStartFiles(AProject: TLazProject) : TM
 
 Var
   I : Integer;
-  E,FN : String;
+  FN : String;
 
 begin
   if Assigned(FTemplate) then
@@ -382,8 +381,7 @@ begin
     For I:=0 to FTemplate.FileCount-1 do
       begin
       FN:=FTemplate.FileNames[I];
-      E:=ExtractFileExt(FN);
-      If (FIgnoreExts.IndexOf(E)=-1) then
+      If (FIgnoreExts.IndexOf(ExtractFileExt(FN))=-1) then
         begin
         FN:=FProjectDirectory+FTemplate.TargetFileName(FN,FVariables);
         LazarusIDE.DoOpenEditorFile(FN, -1, -1, [ofProjectLoading,ofQuiet,ofAddToProject]);
diff --git a/components/sqldb/registersqldb.pas b/components/sqldb/registersqldb.pas
index e4d0d95c40..250ee79b17 100644
--- a/components/sqldb/registersqldb.pas
+++ b/components/sqldb/registersqldb.pas
@@ -108,8 +108,8 @@ uses
   {$ENDIF}
   propedits,
   sqlstringspropertyeditordlg,
-  controls,
-  forms,
+  controls, forms,
+  LazFileUtils,
   {$IFDEF HASLIBLOADER}
     sqldblib,
   {$ENDIF}
@@ -665,7 +665,6 @@ function TSQLSyntaxChecker.CheckSource(Sender: TObject; var Handled: boolean
 
 Var
   AE : TSourceEditorInterface;
-  E : String;
   S : TStringStream;
 
 begin
@@ -675,9 +674,8 @@ begin
   AE:=SourceEditorManagerIntf.ActiveEditor;
   If (AE<>Nil) then
     begin
-    E:=ExtractFileExt(AE.FileName);
     FSFN:=ExtractFileName(AE.FileName);
-    Handled:=CompareText(E,'.sql')=0;
+    Handled:=FilenameExtIs(AE.FileName,'sql');
     If Handled then
       begin
       S:=TStringStream.Create(AE.SourceText);
diff --git a/components/turbopower_ipro/iputils.pas b/components/turbopower_ipro/iputils.pas
index 70bb9b6f17..4389d31eee 100644
--- a/components/turbopower_ipro/iputils.pas
+++ b/components/turbopower_ipro/iputils.pas
@@ -2632,16 +2632,14 @@ var
   Reg : TRegistry;
   Ext : string;
   {$ifndef MSWindows}
-  ExtU: string;
   i : integer;
   {$ENDIF}
 begin
   Result := '';
   Ext := ExtractFileExt(TheFileName);
   {$ifndef MSWindows}
-  ExtU := AnsiLowerCase(Ext);
   for i := 0 to high(MimeTypeExt) do
-    if MimeTypeExt[i] = ExtU then
+    if CompareText(MimeTypeExt[i], Ext) = 0 then
     begin
       result := MimeTypes[i];
       break;
diff --git a/components/wiki/lazwiki/wikiformat.pas b/components/wiki/lazwiki/wikiformat.pas
index 5bbdcae782..4bf44a2877 100644
--- a/components/wiki/lazwiki/wikiformat.pas
+++ b/components/wiki/lazwiki/wikiformat.pas
@@ -385,15 +385,13 @@ end;
 
 function WikiFilenameToPage(Filename: string): string;
 var
-  Ext: String;
   p: Integer;
 begin
   Result:=ExtractFileName(Filename);
   if Result='' then exit;
   // delete .xml
-  Ext:=lowercase(ExtractFileExt(Result));
-  if Ext='.xml' then
-    Result:=LeftStr(Result,length(Result)-length(Ext));
+  if FilenameExtIs(Result,'.xml') then
+    Result:=LeftStr(Result,length(Result)-4);
   // delete case id
   p:=length(Result);
   while (p>=1) and (Result[p] in ['0'..'9','a'..'z']) do
diff --git a/converter/convertdelphi.pas b/converter/convertdelphi.pas
index 2e6002e71d..d8c14cefbe 100644
--- a/converter/convertdelphi.pas
+++ b/converter/convertdelphi.pas
@@ -991,7 +991,7 @@ var
   StartTime, EndTime: TDateTime;
   s: string;
 begin
-  if CompareFileExtQuick(fSettings.MainFilename,'dproj')=0 then begin
+  if FilenameExtIs(fSettings.MainFilename,'dproj') then begin
     fErrorMsg := lisConvDprojFileNotSupportedYet;
     Exit(mrCancel);
   end;
@@ -1009,7 +1009,7 @@ begin
       fLazPMainFilename:=fSettings.DelphiToLazFilename(fSettings.MainFilename,
                                                        fLazPMainSuffix, false);
       // Find Delphi project / package file name
-      if CompareFileExtQuick(fSettings.MainFilename,fDelphiPSuffix)=0 then
+      if FilenameExtIs(fSettings.MainFilename,fDelphiPSuffix) then
         fDelphiPFilename:=fSettings.MainFilename
       else
         fDelphiPFilename:=ChangeFileExt(fSettings.MainFilename,fDelphiPSuffix);
diff --git a/converter/usedunits.pas b/converter/usedunits.pas
index aa5b351492..d5eb473169 100644
--- a/converter/usedunits.pas
+++ b/converter/usedunits.pas
@@ -35,7 +35,7 @@ uses
   // LCL
   Forms, Controls,
   // LazUtils
-  AvgLvlTree,
+  LazFileUtils, AvgLvlTree,
   // codetools
   StdCodeTools, CodeTree, CodeAtom, CodeCache,
   LinkScanner, KeywordFuncLists, SourceChanger, CodeToolsStrConsts,
@@ -521,11 +521,9 @@ end;
 
 function TMainUsedUnits.UsesSectionNode: TCodeTreeNode;
 var
-  s: String;
   IsPackage: Boolean;
 begin
-  s:=ExtractFileExt(fOwnerTool.fFilename);
-  IsPackage := (s='.dpk') or (s='.lpk');
+  IsPackage := FilenameExtIn(fOwnerTool.fFilename,['.dpk','.lpk'],True);
   Result:=fCTLink.CodeTool.FindMainUsesNode(IsPackage);
 end;
 
diff --git a/examples/codepageconverter/mainunit.pas b/examples/codepageconverter/mainunit.pas
index 244c5cb0b8..fbcb02dacf 100644
--- a/examples/codepageconverter/mainunit.pas
+++ b/examples/codepageconverter/mainunit.pas
@@ -226,7 +226,7 @@ begin
       end;
       if ok then
       begin
-        if CompareFileExtQuick(FileListBox1.Items[i], 'lrs') = 0 then
+        if FilenameExtIs(FileListBox1.Items[i], 'lrs') then
         begin
           if ConvertMeLRS(tmp) then
           begin
diff --git a/ide/buildlazdialog.pas b/ide/buildlazdialog.pas
index fb29091983..e27660e9d4 100644
--- a/ide/buildlazdialog.pas
+++ b/ide/buildlazdialog.pas
@@ -275,7 +275,6 @@ end;
 procedure TLazarusBuilder.CleanDir(Dir: string; Recursive: boolean = true);
 var
   FileInfo: TSearchRec;
-  Ext: String;
   Filename: TFilename;
 begin
   Dir:=AppendPathDelim(TrimFilename(Dir));
@@ -292,8 +291,7 @@ begin
           CleanDir(Filename)
       end
       else begin
-        Ext:=LowerCase(ExtractFileExt(FileInfo.Name));
-        if (Ext='.ppu') or (Ext='.o') or (Ext='.rst') or (Ext='.rsj') then begin
+        if FilenameExtIn(FileInfo.Name,['.ppu','.o','.rst','.rsj']) then begin
           if not DeleteFileUTF8(Filename) then
             debugln(['Error : (lazarus) Clean directory: failed to delete file "',Filename,'"']);
         end;
diff --git a/ide/buildmanager.pas b/ide/buildmanager.pas
index 44d7b74517..b0d3a5640e 100644
--- a/ide/buildmanager.pas
+++ b/ide/buildmanager.pas
@@ -872,7 +872,7 @@ procedure TBuildManager.RescanCompilerDefines(ResetBuildTarget,
     if ConfigCache.Units=nil then exit;
     AFilename:=ConfigCache.Units['system'];
     if AFilename='' then exit;
-    if CompareFileExt(AFilename,'ppu',true)<>0 then exit;
+    if not FilenameExtIs(AFilename,'ppu',true) then exit;
     Result:=true;
   end;
 
@@ -1537,7 +1537,7 @@ function TBuildManager.CheckAmbiguousSources(const AFilename: string;
   end;
 
 var
-  Ext, LowExt: string;
+  LowExt: string;
   i: integer;
 begin
   Result:=mrOk;
@@ -1546,8 +1546,7 @@ begin
   and not Compiling then exit;
 
   if FilenameHasPascalExt(AFilename) then begin
-    Ext:=ExtractFileExt(AFilename);
-    LowExt:=lowercase(Ext);
+    LowExt:=lowercase(ExtractFileExt(AFilename));
     for i:=Low(PascalFileExt) to High(PascalFileExt) do begin
       if LowExt<>PascalFileExt[i] then begin
         Result:=CheckFile(ChangeFileExt(AFilename,PascalFileExt[i]));
@@ -1688,7 +1687,7 @@ begin
             or ((FileInfo.Attr and faDirectory)<>0) then continue;
             if FilenameHasPascalExt(FileInfo.Name) then
               CurUnitTree:=SourceUnitTree
-            else if (CompareFileExt(FileInfo.Name,CompiledExt,true)=0) then
+            else if FilenameExtIs(FileInfo.Name,CompiledExt,true) then
               CurUnitTree:=CompiledUnitTree
             else
               continue;
diff --git a/ide/checkcompileropts.pas b/ide/checkcompileropts.pas
index 175d3c5d45..34d695d8a5 100644
--- a/ide/checkcompileropts.pas
+++ b/ide/checkcompileropts.pas
@@ -476,7 +476,7 @@ begin
           if (FileInfo.Name='.') or (FileInfo.Name='..') or (FileInfo.Name='') then
             continue;
           // check extension
-          if CompareFileExt(FileInfo.Name,'ppu',true)=0 then
+          if FilenameExtIs(FileInfo.Name,'ppu',true) then
             Result.Add(Directory+FileInfo.Name);
         until FindNextUTF8(FileInfo)<>0;
       end;
@@ -625,7 +625,7 @@ begin
     Node:=CfgCache.Units.Tree.FindLowest;
     while Node<>nil do begin
       Item:=PStringToStringItem(Node.Data);
-      if (Item^.Value<>'') and (CompareFileExt(Item^.Value,'ppu',true)=0) then
+      if (Item^.Value<>'') and FilenameExtIs(Item^.Value,'ppu',true) then
         CheckFileAge(Item^.Value);
       Node:=CfgCache.Units.Tree.FindSuccessor(Node);
     end;
@@ -804,9 +804,7 @@ begin
         if (FileInfo.Name='.') or (FileInfo.Name='..') or (FileInfo.Name='') then
           continue;
         // check extension
-        if (CompareFileExt(FileInfo.Name,'ppu',true)<>0)
-        and (CompareFileExt(FileInfo.Name,'o',true)<>0)
-        then
+        if not FilenameExtIn(FileInfo.Name, ['ppu','o'], true) then
           continue;
         PPUFiles.Add(Directory+FileInfo.Name);
       until FindNextUTF8(FileInfo)<>0;
diff --git a/ide/codebrowser.pas b/ide/codebrowser.pas
index 151d0ccf4d..fb128217bc 100644
--- a/ide/codebrowser.pas
+++ b/ide/codebrowser.pas
@@ -1387,7 +1387,7 @@ var
     while Node<>nil do begin
       Item:=PStringToStringItem(Node.Data);
       Filename:=Item^.Value;
-      if (CompareFileExt(Filename,'ppu',true)=0) then begin
+      if FilenameExtIs(Filename,'ppu',true) then begin
         // search source in fpc sources
         Filename:=UnitSet.GetUnitSrcFile(ExtractFileNameOnly(Filename));
       end;
diff --git a/ide/compileroptions.pp b/ide/compileroptions.pp
index 67711750ea..5889d45cc3 100644
--- a/ide/compileroptions.pp
+++ b/ide/compileroptions.pp
@@ -1948,7 +1948,7 @@ var
 begin
   if ExtractFileName(aFilename)='' then exit;
   Ext:=GetTargetFileExt;
-  if (Ext<>'') and (CompareFileExtQuick(aFilename,Ext)<>0) then
+  if (Ext<>'') and not FilenameExtIs(aFilename,Ext) then
     aFilename:=aFilename+Ext;
   //DebugLn('Filename is ',AFilename,' in AppendDefaultExt');
 end;
diff --git a/ide/etfpcmsgparser.pas b/ide/etfpcmsgparser.pas
index c624f9a122..cf2ca013fb 100644
--- a/ide/etfpcmsgparser.pas
+++ b/ide/etfpcmsgparser.pas
@@ -1894,7 +1894,7 @@ begin
   begin
     MsgLine.Urgency:=mluVerbose;
   end else if HideHintsUnitNotUsedInMainSource then begin
-    if CompareFileExt(MsgLine.Filename, 'lpr', true)=0 then
+    if FilenameExtIs(MsgLine.Filename, 'lpr', true) then
       // a lpr does not use a unit => not important
       MsgLine.Urgency:=mluVerbose
     else if FilenameIsAbsolute(MsgLine.Filename)
diff --git a/ide/etmakemsgparser.pas b/ide/etmakemsgparser.pas
index ea261cf2a1..76b558b032 100644
--- a/ide/etmakemsgparser.pas
+++ b/ide/etmakemsgparser.pas
@@ -352,7 +352,7 @@ begin
       System.Move(p^,Filename[1],length(Filename));
       Filename:=TrimFilename(Filename);
       if FilenameIsAbsolute(Filename)
-      and ((GetExeExt='') or (ExtractFileExt(Filename)=GetExeExt))
+      and ( (GetExeExt='') or FilenameExtIs(Filename,GetExeExt) )
       and IsFileExecutable(Filename) then begin
         Handled:=true;
         MsgLine:=CreateMsgLine(OutputIndex);
diff --git a/ide/ideprocs.pp b/ide/ideprocs.pp
index 6dcdb299da..7c224b6807 100644
--- a/ide/ideprocs.pp
+++ b/ide/ideprocs.pp
@@ -729,7 +729,7 @@ begin
       if (FileInfo.Name='.') or (FileInfo.Name='..') or (FileInfo.Name='') then
         continue;
       // check extension
-      if CompareFileExt(FileInfo.Name,Ext,false)=0 then begin
+      if FilenameExtIs(FileInfo.Name,Ext,false) then begin
         Result:=AppendPathDelim(Directory)+FileInfo.Name;
         break;
       end;
diff --git a/ide/idetranslations.pas b/ide/idetranslations.pas
index 4ba59b3e7e..697083c400 100644
--- a/ide/idetranslations.pas
+++ b/ide/idetranslations.pas
@@ -209,7 +209,7 @@ var
   i: Integer;
   Item: PItem;
   j: Integer;
-  OutputFilename, OtherRSTFilename, Ext, OtherExt: String;
+  OutputFilename, OtherRSTFilename: String;
 begin
   Result:=true;
   if (RSTDirectory='') or (PODirectory='') then exit;// nothing to do
@@ -236,8 +236,7 @@ begin
     // collect all rst/po files that needs update
     for i:=0 to Files.Count-1 do begin
       RSTFilename:=RSTDirectory+Files[i];
-      Ext:=LowerCase(ExtractFileExt(RSTFilename));
-      if (Ext<>'.rst') and (Ext<>'.rsj') and (Ext<>'.lrj') then
+      if not FilenameExtIn(RSTFilename,['.rst','.rsj','.lrj']) then
         continue;
       if POFilename='' then
         OutputFilename:=PODirectory+ChangeFileExt(Files[i],'.pot')
@@ -260,24 +259,23 @@ begin
       end else begin
         // there is already a source file for this .po file
         //debugln(['ConvertRSTFiles found another source: ',RSTFilename]);
-        if (Ext='.rsj') or (Ext='.rst') or (Ext='.lrj') then begin
-          // rsj are created by FPC 2.7.1+, rst by older => use only the newest
-          for j:=Item^.RSTFileList.Count-1 downto 0 do begin
-            OtherRSTFilename:=Item^.RSTFileList[j];
-            //debugln(['ConvertRSTFiles old: ',OtherRSTFilename]);
-            OtherExt:=LowerCase(ExtractFileExt(OtherRSTFilename));
-            if (OtherExt='.rsj') or (OtherExt='.rst') or (OtherExt='.lrj') then begin
-              if FileAgeCached(RSTFilename)<=FileAgeCached(OtherRSTFilename) then
-              begin
-                // this one is older => skip
-                //debugln(['ConvertRSTFiles ',RSTFilename,' is older => skip']);
-                RSTFilename:='';
-                break;
-              end else begin
-                // this one is newer
-                //debugln(['ConvertRSTFiles ',RSTFilename,' is newer => ignoring old']);
-                Item^.RSTFileList.Delete(j);
-              end;
+        // Already checked earlier.
+        Assert(FilenameExtIn(RSTFilename,['.rst','.rsj','.lrj']), 'ConvertRSTFiles: Wrong Ext');
+        // rsj are created by FPC 2.7.1+, rst by older => use only the newest
+        for j:=Item^.RSTFileList.Count-1 downto 0 do begin
+          OtherRSTFilename:=Item^.RSTFileList[j];
+          //debugln(['ConvertRSTFiles old: ',OtherRSTFilename]);
+          if FilenameExtIn(OtherRSTFilename,['.rsj','.rst','.lrj']) then begin
+            if FileAgeCached(RSTFilename)<=FileAgeCached(OtherRSTFilename) then
+            begin
+              // this one is older => skip
+              //debugln(['ConvertRSTFiles ',RSTFilename,' is older => skip']);
+              RSTFilename:='';
+              break;
+            end else begin
+              // this one is newer
+              //debugln(['ConvertRSTFiles ',RSTFilename,' is newer => ignoring old']);
+              Item^.RSTFileList.Delete(j);
             end;
           end;
         end;
@@ -383,11 +381,11 @@ begin
     // Update po file with lrj or/and rst/rsj files
     for i:=0 to SrcFiles.Count-1 do begin
       Filename:=SrcFiles[i];
-      if CompareFileExtQuick(Filename,'lrj')=0 then
+      if FilenameExtIs(Filename,'lrj') then
         FileType:=stLrj
-      else if CompareFileExtQuick(Filename,'rst')=0 then
+      else if FilenameExtIs(Filename,'rst') then
         FileType:=stRst
-      else if CompareFileExtQuick(Filename,'rsj')=0 then
+      else if FilenameExtIs(Filename,'rsj') then
         FileType:=stRsj
       else
         continue;
diff --git a/ide/imexportcompileropts.pas b/ide/imexportcompileropts.pas
index ee84c0fb1f..2b3ac70774 100644
--- a/ide/imexportcompileropts.pas
+++ b/ide/imexportcompileropts.pas
@@ -204,7 +204,7 @@ begin
   else begin
     // default: depending on file type
     Result:=DefaultCompilerOptPath;
-    if CompareFileExt(fXMLConfig.Filename,'lpk',true)=0 then
+    if FilenameExtIs(fXMLConfig.Filename,'lpk',true) then
     begin
       try
         FileVersion:=fXMLConfig.GetValue(PkgVersionPath,2);
diff --git a/ide/initialsetupproc.pas b/ide/initialsetupproc.pas
index 73bf54bbb5..16580c8580 100644
--- a/ide/initialsetupproc.pas
+++ b/ide/initialsetupproc.pas
@@ -327,7 +327,7 @@ var
   function CheckPPU(const AnUnitName: string): boolean;
   begin
     if (CfgCache.Units=nil)
-    or (CompareFileExt(CfgCache.Units[AnUnitName],'ppu',true)<>0) then
+    or not FilenameExtIs(CfgCache.Units[AnUnitName],'ppu',true) then
     begin
       Note:=Format(lisPpuNotFoundCheckYourFpcCfg, [AnUnitName]);
       Result:=false;
diff --git a/ide/inspectchksumchangeddlg.pas b/ide/inspectchksumchangeddlg.pas
index 953e806e5d..847f604eb3 100644
--- a/ide/inspectchksumchangeddlg.pas
+++ b/ide/inspectchksumchangeddlg.pas
@@ -232,7 +232,6 @@ var
   DirCache: TCTDirectoryCache;
   i: Integer;
   Filename: PChar;
-  Ext: String;
   aFile: TICCFile;
   j: Integer;
 begin
@@ -242,9 +241,8 @@ begin
   if (DirCache=nil) or (DirCache.Listing=nil) then exit;
   for i:=0 to DirCache.Listing.Count-1 do begin
     Filename:=DirCache.Listing.GetFilename(i);
-    Ext:=lowercase(ExtractFileExt(Filename));
-    if ((Ext='.pas') or (Ext='.pp') or (Ext='.p') or (Ext='.ppu'))
-    and (SysUtils.CompareText(anUnitName,ExtractFileNameOnly(Filename))=0)
+    if FilenameExtIn(Filename,['.pas','.pp','.p','.ppu'])
+    and (CompareText(anUnitName,ExtractFileNameOnly(Filename))=0)
     then begin
       j:=Files.Count-1;
       while (j>=0) and (CompareFilenames(Files[j].Filename,Filename)<>0) do
@@ -338,7 +336,7 @@ begin
     FileNode:=nil;
     for i:=0 to Files.Count-1 do begin
       aFile:=Files[i];
-      if CompareFileExt(aFile.Filename,'ppu',true)=0 then
+      if FilenameExtIs(aFile.Filename,'ppu',true) then
         inc(PPUCount)
       else
         inc(SrcCount);
diff --git a/ide/lazbuild.lpr b/ide/lazbuild.lpr
index e53fd0a7fc..ba692a1f62 100644
--- a/ide/lazbuild.lpr
+++ b/ide/lazbuild.lpr
@@ -387,7 +387,7 @@ begin
       Package:=TLazPackageLink(LazPackageLinks.FindLinkWithPkgName(OriginalFileName));
       if Package=nil then begin
         // Not found after everything we tried
-        if CompareFileExt(Filename,'lpi', true)=0 then
+        if FilenameExtIs(Filename,'lpi', true) then
           Error(ErrorFileNotFound,'file not found: '+OriginalFilename)
         else
           Error(ErrorFileNotFound,'package not found: '+OriginalFilename);
@@ -416,15 +416,15 @@ begin
     end
   else begin
     // File exists:
-    if CompareFileExt(Filename,'lpk',true)=0 then begin
+    if FilenameExtIs(Filename,'lpk',true) then begin
       case PackageAction of
       lpaBuild: Result:=BuildPackage(Filename);
       lpaInstall: Result:=true; // this is handled in AddPackagesToInstallList
       lpaAddPkgLinks: Result:=true;
       end;
-    end else if CompareFileExt(Filename,'lpi',true)=0 then
+    end else if FilenameExtIs(Filename,'lpi',true) then
       Result:=BuildProject(Filename)
-    else if CompareFileExt(Filename,'lpr',true)=0 then begin
+    else if FilenameExtIs(Filename,'lpr',true) then begin
       Filename:=ChangeFileExt(Filename,'.lpi');
       if FileExists(Filename) then
         Result:=BuildProject(Filename)
@@ -1058,7 +1058,7 @@ begin
     PkgFilename:='';
     if pvPkgSearch in fPkgGraphVerbosity then
       debugln(['Info: (lazarus) [TLazBuildApplication.AddPackagesToInstallList] "',PackageNamesOrFiles[i],'"']);
-    if CompareFileExt(PackageNamesOrFiles[i],'lpk',true)=0 then
+    if FilenameExtIs(PackageNamesOrFiles[i],'lpk',true) then
       PkgFilename:=ExpandFileNameUTF8(PackageNamesOrFiles[i])
     else if IsValidPkgName(PackageNamesOrFiles[i]) then begin
       PackageLink:=TLazPackageLink(LazPackageLinks.FindLinkWithPkgName(PackageNamesOrFiles[i]));
@@ -1119,7 +1119,7 @@ begin
   begin
     // Look for package name in all known packages
     PkgFilename:=PackageNamesOrFiles[i];
-    if CompareFileExt(PkgFilename,'lpk',true)<>0 then begin
+    if not FilenameExtIs(PkgFilename,'lpk',true) then begin
       ErrorMsg+=PkgFilename+' is not a package (.lpk), so it is not registered.'+LineEnding;
       continue;
     end;
diff --git a/ide/main.pp b/ide/main.pp
index b8333b76c8..34ceb024cf 100644
--- a/ide/main.pp
+++ b/ide/main.pp
@@ -2314,10 +2314,10 @@ begin
   // try command line project
   if (CmdLineFiles<>nil) and (CmdLineFiles.Count>0) then begin
     AProjectFilename:=CmdLineFiles[0];
-    if (CompareFileExt(AProjectFilename,'lpr',true)=0) then
+    if FilenameExtIs(AProjectFilename,'lpr',true) then
       AProjectFilename:=ChangeFileExt(AProjectFilename,'.lpi');
     // only try to load .lpi files, other files are loaded later
-    if (CompareFileExt(AProjectFilename,'lpi',true)=0) then begin
+    if FilenameExtIs(AProjectFilename,'lpi',true) then begin
       AProjectFilename:=CleanAndExpandFilename(AProjectFilename);
       if FileExistsUTF8(AProjectFilename) then begin
         CmdLineFiles.Delete(0);
@@ -2403,7 +2403,7 @@ begin
         // => create a project
         DoNewProject(ProjectDescriptorEmptyProject);
       end;
-      if CompareFileExt(AFilename,'lpk',true)=0 then begin
+      if FilenameExtIs(AFilename,'lpk',true) then begin
         if PkgBoss.DoOpenPackageFile(AFilename,[pofAddToRecent,pofMultiOpen],true)=mrAbort
         then
           break;
@@ -6460,7 +6460,7 @@ begin
   end;
 
   // if there is a project info file, load that instead
-  if CompareFileExtQuick(AFileName, 'lpi') <> 0 then begin
+  if not FilenameExtIs(AFileName, 'lpi') then begin
     LpiFile := ChangeFileExt(AFileName,'.lpi');
     if FileExistsUTF8(LpiFile) then
       AFileName:=LpiFile;   // load instead of program file the project info file
@@ -7103,7 +7103,7 @@ function TMainIDE.CleanUpTestUnitOutputDir(Dir: string): TModalResult;
 var
   Files: TStrings;
   i: Integer;
-  Filename, Ext: String;
+  Filename: String;
 begin
   Dir:=AppendPathDelim(Dir);
   Files:=TStringList.Create;
@@ -7111,10 +7111,7 @@ begin
     CodeToolBoss.DirectoryCachePool.GetListing(Dir,Files,false);
     for i:=0 to Files.Count-1 do begin
       Filename:=Files[i];
-      Ext:=ExtractFileExt(Filename);
-      if (SysUtils.CompareText(Ext,'.ppu')=0)
-      or (SysUtils.CompareText(Ext,'.o')=0)
-      then begin
+      if FilenameExtIn(Filename,['.ppu','.o']) then begin
         Result:=DeleteFileInteractive(Dir+Filename,[]);
         if Result<>mrOk then exit;
       end;
@@ -7556,9 +7553,9 @@ procedure TMainIDE.DoExecuteRemoteControl;
     AProjectFilename:='';
     for i:=Files.Count-1 downto 0 do begin
       AProjectFilename:=Files[0];
-      if (CompareFileExt(AProjectFilename,'lpr',true)=0) then
+      if FilenameExtIs(AProjectFilename,'lpr',true) then
         AProjectFilename:=ChangeFileExt(AProjectFilename,'.lpi');
-      if (CompareFileExt(AProjectFilename,'lpi',true)=0) then begin
+      if FilenameExtIs(AProjectFilename,'lpi',true) then begin
         // open a project
         Files.Delete(i); // remove from the list
         AProjectFilename:=CleanAndExpandFilename(AProjectFilename);
@@ -7587,7 +7584,7 @@ procedure TMainIDE.DoExecuteRemoteControl;
       for i:=0 to Files.Count-1 do begin
         AFilename:=CleanAndExpandFilename(Files.Strings[i]);
         DebugLn(['Hint: (lazarus) TMainIDE.DoExecuteRemoteControl.OpenFiles AFilename="',AFilename,'"']);
-        if CompareFileExt(AFilename,'lpk',true)=0 then begin
+        if FilenameExtIs(AFilename,'lpk',true) then begin
           if PkgBoss.DoOpenPackageFile(AFilename,[pofAddToRecent],true)=mrAbort
           then
             break;
@@ -8893,7 +8890,7 @@ begin
 
   if (ActiveUnitInfo.Component=nil)
   and (ActiveUnitInfo.Source<>nil) then begin
-    if (CompareFileExtQuick(ActiveUnitInfo.Filename,'inc')=0) then begin
+    if FilenameExtIs(ActiveUnitInfo.Filename,'inc') then begin
       // include file => get unit
       UnitCodeBuf:=CodeToolBoss.GetMainCode(ActiveUnitInfo.Source);
       if (UnitCodeBuf<>nil) and (UnitCodeBuf<>ActiveUnitInfo.Source) then begin
@@ -8907,7 +8904,7 @@ begin
         end;
       end;
     end;
-    if (CompareFileExt(ActiveUnitInfo.Filename,'lfm',true)=0) then begin
+    if FilenameExtIs(ActiveUnitInfo.Filename,'lfm',true) then begin
       // lfm file => get unit
       aFilename:=GetUnitFileOfLFM(ActiveUnitInfo.Filename);
       if aFilename<>'' then begin
@@ -12567,7 +12564,7 @@ begin
       end;
     end;
   end
-  else if CompareFileExtQuick(AnUnitInfo.Filename,'inc')=0 then
+  else if FilenameExtIs(AnUnitInfo.Filename,'inc') then
     OkToAdd:=CheckDirIsInSearchPath(AnUnitInfo,True);
   if OkToAdd then
     ;
diff --git a/ide/mainbase.pas b/ide/mainbase.pas
index 36ba036fc2..b016cf1e9d 100644
--- a/ide/mainbase.pas
+++ b/ide/mainbase.pas
@@ -502,7 +502,6 @@ procedure TOpenFileToolButton.RefreshMenu(Sender: TObject);
   procedure AddFile(const AFileName: string; const AOnClick: TNotifyEvent);
   var
     AMenuItem: TOpenFileMenuItem;
-    xExt: string;
   begin
     AMenuItem := TOpenFileMenuItem.Create(DropdownMenu);
     DropdownMenu.Items.Add(AMenuItem);
@@ -510,8 +509,7 @@ procedure TOpenFileToolButton.RefreshMenu(Sender: TObject);
     AMenuItem.FileName := AFileName;
     AMenuItem.Caption := ShortDisplayFilename(AFilename);
     AMenuItem.Hint := AFilename; // Hint is not shown, it just holds the full filename.
-    xExt := ExtractFileExt(AFileName);
-    if SameFileName(xExt, '.lpi') or SameFileName(xExt, '.lpr') then
+    if FilenameExtIn(AFileName,['.lpi','.lpr']) then
       AMenuItem.ImageIndex := LoadProjectIconIntoImages(AFileName, DropdownMenu.Images, FIndex);
   end;
 
diff --git a/ide/sourceeditor.pp b/ide/sourceeditor.pp
index 16f42ed108..4792783b72 100644
--- a/ide/sourceeditor.pp
+++ b/ide/sourceeditor.pp
@@ -6965,8 +6965,7 @@ begin
   CurFilename:=ASrcEdit.FileName;
   ShortFileName:=ExtractFileName(CurFilename);
   MainCodeBuf:=nil;
-  if FilenameHasPascalExt(ShortFileName)
-  or (CompareFileExtQuick(ShortFileName,'inc')=0) then
+  if FilenameHasPascalExt(ShortFileName) or FilenameExtIs(ShortFileName,'inc') then
     MainCodeBuf:=CodeToolBoss.GetMainCode(ASrcEdit.CodeBuffer)
   else if FilenameIsPascalSource(ShortFileName) then
     MainCodeBuf:=ASrcEdit.CodeBuffer;
@@ -6989,16 +6988,14 @@ begin
       MaybeAddPopup('.s');
     end;
     // ToDo: unit resources
-    if (CompareFileExt(ShortFileName,'lfm',true)=0)
-    or (CompareFileExtQuick(ShortFileName,'dfm')=0) then begin
+    if FilenameExtIs(ShortFileName,'lfm',true)
+    or FilenameExtIs(ShortFileName,'dfm') then begin
       MaybeAddPopup('.pas');
       MaybeAddPopup('.pp');
       MaybeAddPopup('.p');
     end;
-    if (CompareFileExt(ShortFileName,'lpi',true)=0)
-    or (CompareFileExt(ShortFileName,'lpk',true)=0) then begin
-      AddContextPopupMenuItem(
-        Format(lisOpenLfm,[ShortFileName]),true,@OnPopupMenuOpenFile);
+    if FilenameExtIn(ShortFileName, ['lpi','lpk'], true) then begin
+      AddContextPopupMenuItem(Format(lisOpenLfm,[ShortFileName]),true,@OnPopupMenuOpenFile);
     end;
     FPDocSrc:=LazarusHelp.GetFPDocFilenameForSource(CurFilename,false,AnOwner);
     if FPDocSrc<>'' then
@@ -8064,10 +8061,9 @@ begin
   aFilename:=copy(aFilename,p,length(aFilename)-(length(ResStr)-2));
   if not FilenameIsAbsolute(aFilename) then
     aFilename:=TrimFilename(ExtractFilePath(GetActiveSE.Filename)+aFilename);
-  if CompareFileExt(aFilename,'lpi',true)=0 then
-    MainIDEInterface.DoOpenProjectFile(aFilename,
-      [ofOnlyIfExists,ofAddToRecent,ofUseCache])
-  else if CompareFileExt(aFilename,'lpk',true)=0 then
+  if FilenameExtIs(aFilename,'lpi',true) then
+    MainIDEInterface.DoOpenProjectFile(aFilename,[ofOnlyIfExists,ofAddToRecent,ofUseCache])
+  else if FilenameExtIs(aFilename,'lpk',true) then
     PackageEditingInterface.DoOpenPackageFile(aFilename,[pofAddToRecent],false)
   else
     MainIDEInterface.DoOpenEditorFile(aFilename,
@@ -10190,8 +10186,7 @@ begin
   CurFilename:=SrcEdit.FileName;
   ShortFileName:=ExtractFileName(CurFilename);
   MainCodeBuf:=nil;
-  if FilenameHasPascalExt(ShortFileName)
-  or (CompareFileExtQuick(ShortFileName,'inc')=0) then
+  if FilenameHasPascalExt(ShortFileName) or FilenameExtIs(ShortFileName,'inc') then
     MainCodeBuf:=CodeToolBoss.GetMainCode(SrcEdit.CodeBuffer)
   else if FilenameIsPascalSource(ShortFileName) then
     MainCodeBuf:=SrcEdit.CodeBuffer;
diff --git a/ide/sourcefilemanager.pas b/ide/sourcefilemanager.pas
index 8c97ae0931..c69f8df116 100644
--- a/ide/sourcefilemanager.pas
+++ b/ide/sourcefilemanager.pas
@@ -1030,7 +1030,7 @@ var
   SourceType: String;
 begin
   if ([ofProjectLoading,ofRegularFile]*FFlags=[]) and (MainIDE.ToolStatus=itNone)
-  and (CompareFileExtQuick(FFilename,'lpi')=0) then begin
+  and FilenameExtIs(FFilename,'lpi',true) then begin
     // this is a project info file -> load whole project
     Result:=MainIDE.DoOpenProjectFile(FFilename,[ofAddToRecent]);
     if Result = mrOK then
@@ -1255,7 +1255,7 @@ begin
   if ([ofRegularFile,ofRevert,ofProjectLoading]*FFlags=[])
   and FilenameIsAbsolute(FFilename) and FileExistsCached(FFilename) then begin
     // check if file is a lazarus project (.lpi)
-    if (CompareFileExt(FFilename,'lpi',true)=0) then
+    if FilenameExtIs(FFilename,'lpi',true) then
     begin
       case
         IDEQuestionDialog(lisOpenProject, Format(lisOpenTheProject, [FFilename]),
@@ -1273,7 +1273,7 @@ begin
     end;
 
     // check if file is a lazarus package (.lpk)
-    if (CompareFileExt(FFilename,'lpk',true)=0) then
+    if FilenameExtIs(FFilename,'lpk',true) then
     begin
       case
         IDEQuestionDialog(lisOpenPackage,
@@ -1851,7 +1851,7 @@ begin
     OkToAdd:=True;
     if IsPascal then
       OkToAdd:=CheckDirIsInSearchPath(ActiveUnitInfo,False)
-    else if CompareFileExtQuick(ActiveUnitInfo.Filename,'inc')=0 then
+    else if FilenameExtIs(ActiveUnitInfo.Filename,'inc') then
       OkToAdd:=CheckDirIsInSearchPath(ActiveUnitInfo,True);
     if OkToAdd then begin
       ActiveUnitInfo.IsPartOfProject:=true;
@@ -4140,7 +4140,7 @@ begin
                           +dlgFilterAll+'|'+GetAllFilesMask;
       if OpenDialog.Execute then begin
         AFilename:=GetPhysicalFilenameCached(ExpandFileNameUTF8(OpenDialog.Filename),false);
-        if CompareFileExt(AFilename,'lpi',true)<>0 then begin
+        if not FilenameExtIs(AFilename,'lpi',true) then begin
           // not a lpi file
           // check if it is a program source
 
@@ -5779,9 +5779,9 @@ begin
   end;
 
   // check, if a .lfm file is opened in the source editor
-  if (LFMUnitInfo=nil) or
-    ((CompareFileExt(LFMUnitInfo.Filename,'lfm',true)<>0) and
-     (CompareFileExtQuick(LFMUnitInfo.Filename,'dfm')<>0)) then
+  if (LFMUnitInfo=nil)
+  or not ( FilenameExtIs(LFMUnitInfo.Filename,'lfm',true) or
+           FilenameExtIs(LFMUnitInfo.Filename,'dfm') ) then
   begin
     if not Quiet then
     begin
@@ -6381,7 +6381,7 @@ begin
     end;
   end;
   try
-    if (CompareFileExt(LFMFilename,'lfm',true)<>0) then
+    if not FilenameExtIs(LFMFilename,'lfm',true) then
     begin
       // no lfm format -> keep old info
       exit(true);
@@ -7403,7 +7403,7 @@ begin
           // Do not care if this fails. A user may have removed the line from source.
           Project1.RemoveCreateFormFromProjectFile(AnUnitInfo.ComponentName);
       end;
-      if CompareFileExtQuick(AnUnitInfo.Filename,'inc')=0 then
+      if FilenameExtIs(AnUnitInfo.Filename,'inc') then
         // include file
         if FilenameIsAbsolute(AnUnitInfo.Filename) then
           ObsoleteIncPaths:=MergeSearchPaths(ObsoleteIncPaths,UnitPath);
@@ -7417,7 +7417,7 @@ begin
         UnitPath:=ChompPathDelim(ExtractFilePath(AnUnitInfo.Filename));
         if FilenameIsPascalUnit(AnUnitInfo.Filename) then
           ObsoleteUnitPaths:=RemoveSearchPaths(ObsoleteUnitPaths,UnitPath);
-        if CompareFileExtQuick(AnUnitInfo.Filename,'inc')=0 then
+        if FilenameExtIs(AnUnitInfo.Filename,'inc') then
           ObsoleteIncPaths:=RemoveSearchPaths(ObsoleteIncPaths,UnitPath);
       end;
       AnUnitInfo:=AnUnitInfo.NextPartOfProject;
diff --git a/ide/transfermacros.pp b/ide/transfermacros.pp
index f6948baf1f..77fa056e84 100644
--- a/ide/transfermacros.pp
+++ b/ide/transfermacros.pp
@@ -481,11 +481,8 @@ end;
 
 function TTransferMacroList.MF_NameOnly(const Filename:string;
   const Data: PtrInt; var Abort: boolean):string;
-var Ext:string;
 begin
-  Result:=ExtractFileName(Filename);
-  Ext:=ExtractFileExt(Result);
-  Result:=copy(Result,1,length(Result)-length(Ext));
+  Result:=ChangeFileExt(ExtractFileName(Filename),'');
 end;
 
 function TTransferMacroList.MF_MakeDir(const Filename: string;
diff --git a/lcl/lresources.pp b/lcl/lresources.pp
index 3d0abbea16..4c1ef594e2 100644
--- a/lcl/lresources.pp
+++ b/lcl/lresources.pp
@@ -1363,7 +1363,7 @@ function LFMtoLRSfile(const LFMfilename: string):boolean;
 var
   LFMFileStream, LRSFileStream: TFileStream;
   LFMMemStream, LRSMemStream: TMemoryStream;
-  LRSfilename, LFMfilenameExt: string;
+  LRSfilename: string;
 begin
   Result:=true;
   try
@@ -1374,9 +1374,7 @@ begin
       LFMMemStream.SetSize(LFMFileStream.Size);
       LFMMemStream.CopyFrom(LFMFileStream,LFMFileStream.Size);
       LFMMemStream.Position:=0;
-      LFMfilenameExt:=ExtractFileExt(LFMfilename);
-      LRSfilename:=copy(LFMfilename,1,
-                    length(LFMfilename)-length(LFMfilenameExt))+'.lrs';
+      LRSfilename:=ChangeFileExt(LFMfilename,'.lrs');
       Result:=LFMtoLRSstream(LFMMemStream,LRSMemStream);
       if not Result then exit;
       LRSMemStream.Position:=0;
diff --git a/packager/interpkgconflictfiles.pas b/packager/interpkgconflictfiles.pas
index a9fd84cf9b..d9b31e6070 100644
--- a/packager/interpkgconflictfiles.pas
+++ b/packager/interpkgconflictfiles.pas
@@ -141,7 +141,6 @@ type
 function CheckInterPkgFiles(IDEObject: TObject;
   PkgList: TFPList; out FilesChanged: boolean
   ): boolean; // returns false if user cancelled
-function FilenameIsCompiledSource(aFilename: string): boolean;
 
 implementation
 
@@ -175,6 +174,11 @@ begin
   Result:=CompareText(F1.ShortFilename,F2.ShortFilename);
 end;
 
+function FilenameIsCompiledSource(aFilename: string): boolean;
+begin
+  Result:=FilenameExtIn(aFilename,['.ppu','.o','.rst','.rsj']);
+end;
+
 { TPGIPAmbiguousFileGroup }
 
 function TPGIPAmbiguousFileGroup.Add(SrcFile, PPUFile: TPGInterPkgFile): integer;
@@ -623,7 +627,6 @@ var
   var
     Files: TStrings;
     aFilename: String;
-    Ext: String;
     AnUnitName: String;
     NewFile: TPGInterPkgFile;
   begin
@@ -642,18 +645,16 @@ var
       begin
         if (aFilename='') or (aFilename='.') or (aFilename='..') then continue;
         if CompareFilenames(aFilename,'fpmake.pp')=0 then continue;
-        Ext:=LowerCase(ExtractFileExt(aFilename));
         AnUnitName:='';
-        case Ext of
-        '.ppu','.o','.rst','.rsj','.pas','.pp','.p':
-          begin
-            AnUnitName:=ExtractFileNameOnly(aFilename);
-            if not IsDottedIdentifier(AnUnitName) then continue;
-          end;
-        '.inc', '.lfm', '.dfm': ;
+        if FilenameExtIn(aFilename,['.ppu','.o','.rst','.rsj','.pas','.pp','.p']) then
+        begin
+          AnUnitName:=ExtractFileNameOnly(aFilename);
+          if not IsDottedIdentifier(AnUnitName) then continue;
+        end
+        else if FilenameExtIn(aFilename,['.inc', '.lfm', '.dfm']) then
+        begin {Do nothing} end
         else
           continue;
-        end;
         NewFile:=TPGInterPkgFile.Create(AppendPathDelim(Dir)+aFilename,
                                         AnUnitName,OwnerInfo);
         FullFiles.Add(NewFile);
@@ -710,7 +711,7 @@ var
       Node:=Node.Successor;
       OFile:=TPGInterPkgFile(ONode.Data);
       if not FilenameIsCompiledSource(OFile.ShortFilename) then continue;
-      if CompareFileExt(OFile.ShortFilename,'ppu',true)=0 then continue;
+      if FilenameExtIs(OFile.ShortFilename,'ppu',true) then continue;
       // search corresponding .ppu
       PPUFileName:=ChangeFileExt(OFile.FullFilename,'.ppu');
       SearchFile:=TPGInterPkgFile.Create(PPUFileName,'',nil);
@@ -1093,13 +1094,5 @@ begin
   end;
 end;
 
-function FilenameIsCompiledSource(aFilename: string): boolean;
-var
-  Ext: String;
-begin
-  Ext:=lowercase(ExtractFileExt(aFilename));
-  Result:=(Ext='.ppu') or (Ext='.o') or (Ext='.rst') or (Ext='.rsj');
-end;
-
 end.
 
diff --git a/packager/lpkcache.pas b/packager/lpkcache.pas
index 9590a70459..f9d12bf616 100644
--- a/packager/lpkcache.pas
+++ b/packager/lpkcache.pas
@@ -310,7 +310,7 @@ var
 begin
   Result:=false;
   if not FilenameIsAbsolute(LPKFilename) then exit;
-  if CompareFilenames(ExtractFileExt(LPKFilename),'.lpk')<>0 then exit;
+  if not FilenameExtIs(LPKFilename,'.lpk') then exit;
   PkgName:=ExtractFileNameOnly(LPKFilename);
   if not IsValidPkgName(PkgName) then exit;
   Result:=true;
diff --git a/packager/packagedefs.pas b/packager/packagedefs.pas
index ddb8430ebf..160580444a 100644
--- a/packager/packagedefs.pas
+++ b/packager/packagedefs.pas
@@ -901,13 +901,13 @@ var
 begin
   HasName:=ExtractFileNameOnly(AFilename)<>'';
   if HasName then begin
-    if CompareFileExt(AFilename,'lfm',true)=0 then
+    if FilenameExtIs(AFilename,'lfm',true) then
       exit(pftLFM)
-    else if CompareFileExt(AFilename,'lrs',true)=0 then
+    else if FilenameExtIs(AFilename,'lrs',true) then
       exit(pftLRS)
-    else if CompareFileExtQuick(AFilename,'inc')=0 then
+    else if FilenameExtIs(AFilename,'inc') then
       exit(pftInclude)
-    else if CompareFileExtQuick(AFilename,'xml')=0 then
+    else if FilenameExtIs(AFilename,'xml') then
       exit(pftIssues)
     else if FilenameHasPascalExt(AFilename) then begin
       Result:=pftUnit;
@@ -2072,8 +2072,8 @@ var
 begin
   Result:='';
   AFilename:=TrimFilename(DefaultFilename);
-  if (CompareFileExt(AFilename,'lpk',true)<>0)
-  or (SysUtils.CompareText(ExtractFileNameOnly(AFilename),PackageName)<>0) then
+  if not FilenameExtIs(AFilename,'lpk',true)
+  or (CompareText(ExtractFileNameOnly(AFilename),PackageName)<>0) then
     exit;
   if not FilenameIsAbsolute(AFilename) then begin
     CurDir:=GetDependencyOwnerDirectory(Self);
diff --git a/packager/packagelinks.pas b/packager/packagelinks.pas
index dc7c067072..c95e82fd10 100644
--- a/packager/packagelinks.pas
+++ b/packager/packagelinks.pas
@@ -392,7 +392,7 @@ procedure TLazPackageLinks.UpdateGlobalLinks;
   begin
     Result:=false;
     PkgName:='';
-    if CompareFileExt(Filename,'lpl',true)<>0 then exit;
+    if not FilenameExtIs(Filename,'lpl',true) then exit;
     StartPos:=1;
     // parse identifier
     if (StartPos>length(Filename))
@@ -463,7 +463,7 @@ begin
     LazDir:=EnvironmentOptions.GetParsedLazarusDirectory;
     for i:=0 to Files.Count-1 do begin
       LPLFilename:=GlobalLinksDir+Files[i];
-      if CompareFileExt(LPLFilename,'lpl',true)<>0 then continue;
+      if not FilenameExtIs(LPLFilename,'lpl',true) then continue;
       if (not ParseFilename(Files[i],NewPkgName,PkgVersion))
       then begin
         DebugLn('Warning: (lazarus) suspicious pkg link file found (name): ',LPLFilename);
diff --git a/tools/lplupdate.lpr b/tools/lplupdate.lpr
index a484da7373..bfa6d91a1b 100644
--- a/tools/lplupdate.lpr
+++ b/tools/lplupdate.lpr
@@ -227,7 +227,7 @@ begin
       if (FileInfo.Attr and faDirectory)>0 then begin
         // scan sub directories too
         ScanPackages(AppendPathDelim(Dir+FileInfo.Name),Packages);
-      end else if CompareFileExt(FileInfo.Name,'lpk',true)=0 then begin
+      end else if FilenameExtIs(FileInfo.Name,'lpk',true) then begin
         ScanPackage(Dir+FileInfo.Name,Packages);
       end;
     until FindNextUTF8(FileInfo)<>0;
@@ -272,7 +272,7 @@ begin
         continue;
       if (FileInfo.Attr and faDirectory)>0 then begin
         // skip
-      end else if CompareFileExt(FileInfo.Name,'lpl',true)=0 then begin
+      end else if FilenameExtIs(FileInfo.Name,'lpl',true) then begin
         ScanLink(Dir+FileInfo.Name,Links);
       end;
     until FindNextUTF8(FileInfo)<>0;