A wordfilter (sometimes referred to as just "filter" or "censor") is a script typically used on Internet forums or chat rooms that automatically scans users' posts or comments as they are submitted and automatically changes or censors particular words or phrases. The most basic wordfilters search only for specific strings of letters, and remove or overwrite them regardless of their context. More advanced wordfilters make some exceptions for context (such as filtering "butt" but not "butter"), and the most advanced wordfilters may use regular expressions.