Debug: $wgDebugToolbar
Display the debugging toolbar
Introduced in version:1.19.0
Removed in version:still in use
Allowed values:(boolean)
Default value:false

Details edit

Displays the debugging toolbar. This also enables profiling on database queries and other useful output. This must remain "false" in production to avoid exposing private information.

The debug toolbar will not be displayed when either $wgUseFileCache or $wgUseSquid /$wgUseCdn are set to "true".