Manual:$wgMaxSigChars

<translate> User accounts, authentication</translate>: $wgMaxSigChars
Maximum wiki code length for customized signatures.
<translate> Introduced in version:</translate>	1.11.0 (r22960)
<translate> Removed in version:</translate>	<translate> still in use</translate>
<translate> Allowed values:</translate>	(integer)
<translate> Default value:</translate>	255
<translate> Other settings:</translate> <translate> Alphabetical</translate> | <translate> By function</translate>

Details

Maximum wiki code length, in characters, for customized signatures. Preview versions of 1.10.0 prior to phab:rMWc52af0da6d7a used UTF-8 bytes instead of characters.

File:OOjs UI icon notice-destructive.svg <translate> Warning:</translate>

This does not consider the length of the substituted templates used in the signature, so although {{subst:<Very long template name>}} will be rejected if the template name has more than $wgMaxSigChars (-10) characters, {{subst:Main page}} will work even if the main page is a lot longer than $wgMaxSigChars (<translate> task <tvar name=1>T12715</tvar></translate>).