An edit summary is a brief explanation of an edit to a Wikipedia page. When you edit a page, there is a small text entry field labeled Edit summary located under the main edit box and above the Publish changes button:
It is good practice to fill in the edit summary field, or add to it in the case of section editing, as this helps others to understand the intention of your edit. Edit summaries are displayed in lists of changes (such as page histories and watchlists), and at the top of diff pages.
It is considered good practice to provide a summary for every edit, especially when reverting (undoing) the actions of other editors or deleting existing text; otherwise, people may question your motives for the edit. Accurate summaries help other contributors decide whether they want to review an edit, and to understand the change should they choose to review it.
Edits that do not have an edit summary are more likely to be reverted incorrectly, because it may not be obvious what the purpose of the edit was. Editors should not revert an otherwise good edit because of a missing or confusing edit summary; good editors may simply have forgotten, or a confusing edit summary may have been the result of an autofill mishap. (If the edit summary itself violates privacy or other policies, see the Fixing section below.) However, realistically, when a major edit (e.g., addition or deletion of a substantial amount of article text, or a substantial rewrite) doesn't have an edit summary, some busy editors might not assume good faith and revert the change without evaluating it properly. Providing an edit summary helps prevent that kind of error.
Summaries are less important for minor changes (which means generally unchallengeable changes, such as spelling or grammar corrections), but a brief note like "fixed spelling" is helpful even then.
To avoid accidentally leaving edit summaries blank, registered editors can select "Prompt me when entering a blank edit summary" on the Editing tab of the user preferences.
Proper use of edit summaries is critical to resolving content disputes. Edit summaries should accurately and succinctly summarize the nature of the edit, especially if it could be controversial. If the edit involves reverting previous changes, it should be marked as a revert ("rv") in the edit summary.
Avoid using edit summaries to carry on debates or negotiation over the content or to express opinions of the other users involved. This creates an atmosphere where the only way to carry on discussion is to revert other editors! If you notice this happening, start a section on the talk page and place your comments there. This keeps discussions and debates away from the article page itself. For example:
After you publish the page, you cannot change the edit summary, so be careful with it, particularly if you are in a heated content dispute – do not write things you will regret.
If you make an important omission or error in an edit summary, you can correct this by making a dummy edit (a change in the page with no visible effects), and adding further information in the dummy edit's summary.
In the extreme case of an edit summary containing certain kinds of harmful content, the summary can be deleted on request. They may be removed from public view by administrators using Revision Deletion; such edit summaries remain visible to administrators. In even more limited circumstances the entire edit may be oversighted, leaving it and its edit summary visible only to the handful of users with the Oversight permission.
The source text of the edit summary can be seen at id, where id is the revision number. For example, says
diff=845523983 in the url so shows the edit summary source. The link uses mw:API:Revisions, which is mainly intended for programs.
When adding a new section to a discussion page with the "new section" button, the section title is used as the edit summary. When editing an existing section, the section title is inserted at the beginning of the edit summary, enclosed with /* and */ marks, for example /* External links */. Details of the edit should be added after this text.
When viewing such an edit summary, the section name will appear in blue, with a small arrow next to it: . Click the arrow or section name to view the section (if the section no longer exists, the link will simply take you to the top of the page).
If you create a new section before or after an existing section by clicking a section "edit" link, delete the text between /* and */ marks (or change it to the new section title) to avoid confusion.
Note: Tools that track edit summary usage by a user (such as ) do not consider the auto-added part as a summary; that's any part within /* and */. You're encouraged to provide real edit summary whether the editbox contains such auto-summary or not.
In certain circumstances, an automatic summary is generated when an edit is published without one. This is slightly different from the summary added when editing a section, as that can be modified by the user before saving.
With the exception of the automatic summary when creating a redirect, which usually says all that needs to be said, these are not a substitute for a proper edit summary – you should always leave a meaningful summary, even in the above cases. They are, however, useful in providing some context for edits made by inexperienced users who are not aware of the importance of edit summaries, and for spotting vandalism.
When starting a new thread on a talk page by using the "New section" tab, the text you type into the "subject/headline" field becomes both the heading of your discussion topic, and the edit summary for that edit.
Tags (i.e., edit tags) are brief messages that the software automatically places next to certain edits in histories, recent changes and other special pages. They are implemented by the edit filter to help assist vandalism patrollers and other page watchers. They cannot be added or removed manually.
The limit of 500 characters is an approximation. The actual limit is 500 Unicode codepoints. Most characters occupy one codepoint, but some characters like those with diacritics or emojis may consist of more than one codepoint. The limit of 500 codepoints includes the section title marker (and the associated
/* */) and also any Wiki markup that may be present.
When the edit is done by a bot, through an external tool (such as WP:AWB) or through some user script or gadget, it's the responsibility of the tool or script to safeguard against overflowing this limit. In any situation where more than 500 codepoints are entered for the edit summary, the summary is truncated to 500 codepoints when the page is published.