On Wikipedia, reverting means undoing or otherwise negating the effects of one or more edits, which restores the page (or a part of it) to a previous version. Partial reversion involves restoring one part of the page to a previous version, but leaving other contributions intact. Self-reversion is the act of reverting your own edits. Reverting does not always involve the use of the undo tool. Any method of editing that has the practical effect of returning some or all of the page to a previous version counts as a reversion.
Reverting a contribution is sometimes appropriate. However, reverting good-faith actions of other editors can also be disruptive and may lead to the reverter being temporarily blocked from editing. The three-revert rule (part of the edit warring policy) limits the number of times an editor can revert edits (including partial reversions) on a page.
Consider very carefully before reverting, as it rejects the contributions of another editor. Consider what you object to, and what the editor was attempting. Can you improve the edit, bringing progress, rather than reverting it? Can you revert only part of the edit, or do you need to revert the whole thing?
In the edit summary or on the talk page, succinctly explain why the change you are reverting was a bad idea or why reverting it is a better idea. In cases of blatant vandalism, uncontroversially disruptive changes or unexplained removals, the amount of explanation needed is minimal. But in the event of a content dispute, a convincing, politely-worded explanation gains much importance and avoids unnecessary disputes.
There are several ways to revert edits. A reversion can be carried out manually by editing the page to delete wrongly added text or restore wrongly deleted text. You can do this by copying and pasting text from a past version.
You can also restore a past version of the page. To do this:
The MediaWiki software sometimes enables editors to easily revert (undo) a single edit from the history of a page, without simultaneously undoing all constructive changes that have been made since. To do this, view the page history or the diff for the edit, then click on "undo" next to the edit in question. The software will attempt to create an edit page with a version of the article in which the undesirable edit has been removed, but all later edits are retained. There is a default edit summary, but this can be modified before saving.
It is also possible to undo several consecutive edits, even if they conflict among themselves: view the "diff" to be removed (by selecting the earliest and most recent revisions in the history and clicking "compare selected revisions"), and click the "undo" link.
By default, undo functionality is not available in Wikipedia's mobile user interface. If advanced mode is enabled, undo is available from history pages, but not from diff pages. See T191706 for discussion. Its full access is also available to mobile users with desktop view enabled.
See also: Wikipedia:Rollback
Administrators and editors who have been granted access to the rollback feature have additional links that:
Rollback links appear on the user contributions pages, user watchlists, recent changes pages, history pages and diff pages. Note that in the last case, rollback links can be misleading, since reversion is not necessarily to the old version shown (the diff page may show the combined result of edits, including some by other editors or only part of the edits the rollback button would revert). To see the changes the rollback button will revert, view the specific diff that compares the last version from the last editor with the last version from the previous editor. Users with Twinkle enabled will also have three buttons which work similar to rollback, but each is used in a different situation;
Rollback AGF is used to revert good-faith edits, so an edit summary is required.
The standard rollback allows doing mostly the same thing, but with an edit summary.
The vandalism button should only be used to revert obvious vandalism, since it only takes a single click and does not require an edit summary.
The rollback button will look similar to this:
[rollback: # edits]
Rollback works much more quickly than undo, since it:
On the other hand, it is not as versatile as undo, since it does not allow specification of which edits have to be undone. One may want to revert more or fewer edits than the rollback does, or edits that do not include the last edit. It also does not allow adding an explanation to the automatic edit summary without external scripts. Rollback without an edit summary may only be used in certain circumstances; most commonly to revert obvious vandalism. Rolling back a good-faith edit or even during an edit war may be interpreted as "I think your edit was no better than vandalism, and reverting it doesn't need an explanation". The rollback right can be revoked on misuse: refer to its main page.
If someone else edited or rolled back the page before you clicked the "rollback" link, or if there was no previous editor, you will get an error message.
In cases of flood vandalism (rapid changes to many articles), administrators, and global rollbackers, may choose to hide vandalism and reverts from recent changes. To do this, add &bot=1 to the end of the URL used to access a user's contributions. For example: http://en.wikipedia.org/w/index.php?title=Special:Contributions&target=SomePersistentVandal&bot=1.
When the rollback links on the contributions list are clicked, the revert and the original edit that you are reverting will both be hidden from recent changes, unless you click the "bots" link in the Recent Changes to set hidebots=0. The edits are not hidden from contributions lists, page histories or watchlists. The edits remain in the database and are not removed, but they no longer flood "Recent changes". The aim of this feature is to reduce the annoyance factor of a flood vandal, with relatively little effort. This should not be used for reverting a change you just don't like, but is meant only for massive floods of simple vandalism.
To revert an image to a previous version, go to the image page and click on "File history."
You will then see a list of past edits and a thumbnail graphic of each. Logged-in users will also see a "Revert" link for versions other than the current one. Click on a Revert link to make the change.
If the image is at Wikimedia Commons you must click through to the image page there to do the revert. Then scroll down to the thumbnails. Beside the thumbnail you wish there will be the word "Revert". You will need to be logged in at Commons.
Ultimately, it is the responsibility of the person reverting edits on the page to be sure that any intervening helpful edits are not reverted, or are re-applied to the article.
In some instances, it is possible to progressively undo changes starting from the most recent and working backward in time, skipping those edits which are not to be reverted. The success of being able to do this will depend on where the various edits are located within the article text. If they overlap or are close together within the text, the software will consider them to be conflicting with more recent edits and not permit an "undo" operation. In some cases, it is easier to begin with this technique as it may revert at least some of the unhelpful edits, providing a point from which it is easier to begin hand editing.
When considering reverting multiple edits, one should examine all the intervening edits. These are often a mix of both helpful and unhelpful edits. The goal is to remove the effect of the unhelpful edits and leave the helpful ones. This can be done either by undoing the unhelpful edits or reverting to a version of the page prior to the beginning of the unhelpful edits and re-applying, by hand, the helpful edits. To re-apply helpful edits, or revert unhelpful edits, it is usually easier to copy-and-paste portions of a version of the article which contains, or does not contain those edits. In complex situations, this may result in combining portions of text from multiple versions of the article. The choice of starting this process from the current version as your base text, or using a prior version as your base will depend on the relative extent and localization within the article text of the changes which are to be kept and those to be reverted. It is usually easier to have the by-hand operation be on localized areas of text, rather than those changes spread throughout an article. This can be a long (hours) and complex process. It can be quite helpful to use the "Show changes" button in the edit window to compare the current diff against a diff, in a different tab or window, of the changes which you are attempting to remove or re-apply.
If you are re-applying edits by other editors, you should state the original author(s) and which edit(s) in your edit summary to provide appropriate credit. If you are reverting to a prior version with the intent of re-applying changes in follow-up edits, you should explicitly say so in the edit summary of your reversion and use the ((in use)) template to indicate to other editors that you are working on the article. This is particularly important because the editors responsible for any edits which you have reverted will immediately be notified that their edit has been reverted. If there is no indication that you are working on the article, particularly if you are working to re-apply helpful edits, the other editors may edit the article in the intervening time, creating an edit conflict. Having an edit reverted can be upsetting to other editors, particularly if considerable time and effort were put into performing the edit. If you are planning to re-apply such edits, it is best to let the editors know that up-front.
The choice of method to use in complex situations is often based on your experience with the process and the available tools. Keep in mind that if you get into a situation which you find difficult to resolve, it is always possible to completely revert your own edit(s) and return the article to the condition in which you found it.