# Module mod_speling

This module attempts to correct misspellings of URLs that users might have entered, by ignoring capitalization and by allowing up to one misspelling.

Status: Extension
Source File: mod_speling.c
Module Identifier: speling_module
Compatibility: Available in Apache 1.3 and later. Available as an External module in Apache 1.1 and later.

## Summary

Requests to documents sometimes cannot be served by the core apache server because the request was misspelled or miscapitalized. This module addresses this problem by trying to find a matching document, even after all other modules gave up. It does its work by comparing each document name in the requested directory against the requested document name without regard to case, and allowing up to one misspelling (character insertion / omission / transposition or wrong character). A list is built with all document names which were matched using this strategy.

If, after scanning the directory,

- no matching document was found, Apache will proceed as usual and return a "document not found" error.
- only one document is found that "almost" matches the request, then it is returned in the form of a redirection response.
- more than one document with a close match was found, then the list of the matches is returned to the client, and the client can select the correct candidate.

## Directives

- CheckSpelling

## CheckSpelling directive

Syntax: CheckSpelling on|off
Default: `CheckSpelling Off`
Context: server config, virtual host, directory, .htaccess
Override: Options
Status: Base
Module: mod_speling
Compatibility: CheckSpelling was available as a separately available module for Apache 1.1, but was limited to miscapitalizations. As of Apache 1.3, it is part of the Apache distribution. Prior to Apache 1.3.2, the `CheckSpelling` directive was only available in the "server" and "virtual host" contexts.

This directive enables or disables the spelling module. When enabled, keep in mind that

- the directory scan which is necessary for the spelling correction will have an impact on the server's performance when many spelling corrections have to be performed at the same time.
- the document trees should not contain sensitive files which could be matched inadvertently by a spelling "correction".
- the module is unable to correct misspelled user names (as in `http://my.host/~apahce/`), just file names or directory names.
- spelling corrections apply strictly to existing files, so a request for the `<Location /status>` may get incorrectly treated as the negotiated file "`/stats.html`".