Automatic edit summaries are created by the MediaWiki software for certain actions. These summaries appear in recent changes, page histories, and contributions lists, unless you provide your own edit summary.

Auto edit summaries exist for several actions, if the user fails to provide an edit summary:

• Blanking a page
• Replacing entire page with other text, removing more than 90% of the content of a page
• Creating a new page (the first 200 characters of the article appear in the summary)
• Adding, changing, or removing a redirect
• Reverting a revision

Additionaly, when you use section editing, the section title will appear in the edit summary box in light grey text between comment tags, and used as your summary unless you alter or replace it.

Typing the summary is unimportant when a user creates a new page; leaving the summary area blank, the edit summary in this case is automatically set to "Created page with", followed by around 200 characters of the entered wikitext (the maximum summary length), with a trailing ellipsis.

If the summary describes a redirect or replacement of the content with a {{copyvio}} template, this most likely means that an editor allowed the software to generate the summary out of convenience. If the listed target or replacement text is reasonable, no further action is required.

A summary indicative of an inappropriate edit (such as the blanking or replacement of legitimate content) is probably not a deliberate description on the part of the user (who might not even have realized that they were harming Wikipedia).

If vandalism (or a well-meaning test requiring reversion) is suspected, please examine the edit to determine its nature and respond accordingly. Remember to assume good faith in the absence of evidence to the contrary. Keep in mind that the edit summary was not typed by the user, so it should not be interpreted as such evidence.

When an anonymous editor blanks all or part of a BLP, this might be the subject attempting to remove problematic material. Edits like these by subjects should not be treated as vandalism; instead, the subject should be invited to explain their concerns.

— WP:BLPEDIT

Automatic edit summaries include the following. The text may be edited by administrators:

Action	Page	Example
Removing all content on a page, resulting in an empty page with no content (criteria: new page size of 0 bytes)	MediaWiki:Autosumm-blank	←Blanked the page
Removing nearly all content on a page, and possibly replacing it with new content (criteria: at least 90% of original content removed, and a new page size not exceeding 1,000 bytes)	MediaWiki:Autosumm-replace	←Replaced content with 'The cat sat on the mat'
Creating a new page with content (criteria: page size greater than 0 bytes)	MediaWiki:Autosumm-new	←Created page with 'The cat sat on the mat'
Creating an empty page with no content (criteria: page size of 0 bytes)	MediaWiki:Autosumm-newblank	←Created blank page
Adding a redirect to another page	MediaWiki:Autoredircomment	←Redirected page to Help:Contents
Changing the target of a redirect	MediaWiki:Autosumm-changed-redirect-target	←Changed redirect target from Help:Contents to Help:Introduction
Removing a redirect from a page	MediaWiki:Autosumm-removed-redirect	←Removed redirect to Help:Contents
Undoing a past revision of the page (by clicking "undo" in the page history)	MediaWiki:Undo-summary	Undid revision 11572 by Example (talk)
Reverting one or more edits to a page by a user (using the rollback feature)	MediaWiki:Revertpage	Reverted edits by Example (talk) to last version by Username

• Feature description at MediaWiki.org
• Undo and rollback, reverting tools that pre-fill the edit summary