Apache Reference: mod_speling

mod_speling - URL Spelling Correction
Since Apache 1.3, src/modules/standard/mod_speling.c
Alexei Kosut, Martin Kraemer (1997)

mod_speling is a very handy module. It corrects minor spelling or capitalization errors in URLs --- indeed its droll name provides a hint as to its task. The module addresses this problem by trying to find a matching document, even after all other modules (such as mod_alias, mod_rewrite, or mod_userdir) give up. It works by comparing each document name in the requested directory against the requested document name without regard to case, allowing a maximum of one misspelling (character insertion, omission, transposition, or wrong character). The drawback of this nice feature is that the complicated disk I/O usually increases the response time. Often, it is a better choice to force the user to fix the reference.