diff --git a/autoninja.bat b/autoninja.bat
index 14e2f4597f..6d7d532072 100755
--- a/autoninja.bat
+++ b/autoninja.bat
@@ -7,18 +7,18 @@ setlocal
 
 set scriptdir=%~dp0
 
-REM Set unique build ID.
+:: Set unique build ID.
 FOR /f "usebackq tokens=*" %%a in (`%scriptdir%python-bin\python3.bat -c "import uuid; print(uuid.uuid4())"`) do set AUTONINJA_BUILD_ID=%%a
 
-REM If a build performance summary has been requested then also set NINJA_STATUS
-REM to trigger more verbose status updates. In particular this makes it possible
-REM to see how quickly process creation is happening - often a critical clue on
-REM Windows. The trailing space is intentional.
-if "%NINJA_SUMMARIZE_BUILD%" == "1" set NINJA_STATUS=[%%r processes, %%f/%%t @ %%o/s : %%es ] 
+:: If a build performance summary has been requested then also set NINJA_STATUS
+:: to trigger more verbose status updates. In particular this makes it possible
+:: to see how quickly process creation is happening - often a critical clue on
+:: Windows. The trailing space is intentional.
+if "%NINJA_SUMMARIZE_BUILD%" == "1" set NINJA_STATUS=[%%r processes, %%f/%%t @ %%o/s : %%es ]
 
 :loop
 IF NOT "%1"=="" (
-    @rem Tell goma or reclient to not do network compiles.
+    :: Tell goma or reclient to not do network compiles.
     IF "%1"=="--offline" (
         SET GOMA_DISABLED=1
         SET RBE_remote_disabled=1
@@ -31,16 +31,16 @@ IF NOT "%1"=="" (
     GOTO :loop
 )
 
-REM Execute whatever is printed by autoninja.py.
-REM Also print it to reassure that the right settings are being used.
-REM Don't use vpython - it is too slow to start.
-REM Don't use python3 because it doesn't work in git bash on Windows and we
-REM should be consistent between autoninja.bat and the autoninja script used by
-REM git bash.
+:: Execute whatever is printed by autoninja.py.
+:: Also print it to reassure that the right settings are being used.
+:: Don't use vpython - it is too slow to start.
+:: Don't use python3 because it doesn't work in git bash on Windows and we
+:: should be consistent between autoninja.bat and the autoninja script used by
+:: git bash.
 FOR /f "usebackq tokens=*" %%a in (`%scriptdir%python-bin\python3.bat %scriptdir%autoninja.py "%*"`) do echo %%a & %%a
 @if errorlevel 1 goto buildfailure
 
-REM Use call to invoke python script here, because we use python via python3.bat.
+:: Use call to invoke python script here, because we use python via python3.bat.
 @if "%NINJA_SUMMARIZE_BUILD%" == "1" call %scriptdir%python-bin\python3.bat %scriptdir%post_build_ninja_summary.py %*
 @call %scriptdir%python-bin\python3.bat %scriptdir%ninjalog_uploader_wrapper.py --cmdline %*
 
@@ -49,6 +49,6 @@ exit /b
 
 @call %scriptdir%python-bin\python3.bat %scriptdir%ninjalog_uploader_wrapper.py --cmdline %*
 
-REM Return an error code of 1 so that if a developer types:
-REM "autoninja chrome && chrome" then chrome won't run if the build fails.
+:: Return an error code of 1 so that if a developer types:
+:: "autoninja chrome && chrome" then chrome won't run if the build fails.
 cmd /c exit 1
diff --git a/update_depot_tools.bat b/update_depot_tools.bat
index 14eaa815dd..5384675b7e 100644
--- a/update_depot_tools.bat
+++ b/update_depot_tools.bat
@@ -13,7 +13,7 @@ setlocal
 IF "%~nx0"=="update_depot_tools.bat" (
   COPY /Y "%~dp0update_depot_tools.bat" "%TEMP%\update_depot_tools_tmp.bat" >nul
   if errorlevel 1 goto :EOF
-  REM Use call/exit to avoid leaving an orphaned window title.
+  :: Use call/exit to avoid leaving an orphaned window title.
   call "%TEMP%\update_depot_tools_tmp.bat" "%~dp0" %*
   exit /b
 )