All versions of an article are stored, so it is easy to revert a bad edit and return the article to its previous state.
- Go to the page, click on "history" at the top ("Page history" in some skins), and click on the time and date of the earlier version you want to revert to. It will not work if you click on 'cur' or 'last'.
- Then when that page comes up, you'll see something like "(Revision as of 23:19 Aug 15, 2002)" below the title.
- Verify that you've selected the correct version, and click to edit the page, as you would normally. Important: in the case of vandalism, take the time to make sure that you are reverting to the last version without the vandalism; there may be multiple vandal edits.
- You'll get a warning, above the edit box, about editing an out-of-date revision.
- After heeding the warning, save the page. Be sure to add the word "revert" to the edit summary (often abbreviated as "rv"). It is common practice to mention the version of the page that you're reverting back to in the description as well, though you don't have to do so.
Non vandal edits can also be reverted if you think an older version of a page is better than the current version. This is done in the same way as described above, but you should take care not to over-write someone's edit without reason. A third version that takes the best bits of the other two, and combines them to get the best of both worlds, will often be preferable to reverting a genuine edit. You should save reverts for cases where the new version is actively worse.
Instead of removing all changes after a certain version, the latest versions of MediaWiki allow a single edit to be undone. To do this, view the diff for the edit, and click on 'undo' above the newer version. The software will attempt to create an edit page with a version of the article in which the undone edit doesn't exist but all later edits are retained. The automatic edit summary added when using the undo feature can be found at MediaWiki:Undo-summary.
This feature removes the need to manually redo useful changes since the "undone" edit. However, it will fail if undoing the edit would conflict with later edits. For example, if edit 1000 adds a paragraph and edit 1005 modifies that paragraph, it will be impossible to automatically undo edit 1000. In this case, you must determine how to resolve the problem manually.
Reverts by administrators
Administrators have a rollback link on diff pages and on user contribution lists that lets them revert vandalism faster.
Clicking on the link reverts to the last edit not authored by the user concerned. An edit summary will be added automatically stating that a reversion was made. The edit will be marked as minor.
In cases of flood vandalism, admins can choose to hide vandalism 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://www.wikia.com/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 the default recent changes display. This means that they will be hidden from recent changes unless you click the "bots" link 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.
Guidelines when reverting
You should always explain why you are reverting an article. This helps the reverted person to fix whatever problem it is that you've identified and explains to other people whether they need to even view the reverted version. If your reasons for reverting are too complex to explain in the edit summary, explain it on the talk page.
Revert wars are not acceptable. High-frequency reversion wars make the page history less useful, waste space in the database, make it hard for other people to contribute, and flood recent changes and watchlists. See the advice on staying cool when the editing gets hot at Wikipedia.