Wikipedia:You can and cannot change Wikipedia

Almost every Wikipedia user, whether they are a registered Wikipedian with an account and password or are just anonymously browsing, sees and can use an edit link on almost every page of the Encyclopedia, and following that link, can change the content of the page.

And these changes are then immediately visible to anyone who views that page. And this applies to our articles, and our policies, and other people's user pages, and many others. Isn't it exciting?

Yes. But... isn't it also suicide?

No. And that is even more exciting! And the whole reason that Wikipedia works.

Wikipedia has page histories. So every time you make a change to an article (or most other pages), the old version is still there too, and is almost as easily accessible to a reader or to another editor as the current version of the page.

And so if you do something silly, someone else can easily undo it. We call this reverting, and it's one reason we encourage you to be bold.

Of course it's not a blank check. Some users waste so much of other people's time that as a last resort we restrict their editing. Some pages attract so much rubbish, or are so critical to the project, that as a last resort we restrict editing of them. Some material is so damaging that we immediately and permanently remove it.

But all of these are rare, and again, that's why Wikipedia works.

Page histories, permalinks and so on
Every wiki page at Wikipedia (which means every editable page, but not special pages) has a page history, a special page that shows a record of both the previous versions of the page and the edits that have been made to it. It shows what was changed, when and by whom. And it links to copies of these past versions.

These edit histories are a vital part of Wikipedia for several reasons. Probably the most important is, they are required by our copyleft licensing. We are obliged to keep records of every text contribution to every article (and to all other pages too but it's the articles that matter). If we fail to do this, we breach our copyright responsibilities. As a result the affected content may not be legally reusable (and that's a real hot button here), and/or we may be in breach of copyright ourselves (and that's another hot button).

But another important result is, any past version in the page history can be viewed and edited, or just saved without editing. And that's almost any past version of the page....Occasionally a version is deliberately removed from the history, see below, but this is rare.

If a past version is saved (with or without editing it), all changes made to the page since the version that was just saved just disappear from the page, so do this with great caution, and only if you are sure you know what you are doing. (But your edit can then itself be reverted, which puts them all back again. It's all in the page history!)

Any version in the page history (including the current one) can also be bookmarked, or linked to from both within Wikipedia and from other websites. These links are called permalinks. They're very useful in talk pages and project pages, but never used in articles. And any version can be reused by other writers, provided they adhere to their own copyright and copyleft obligations... which includes, attributing the copied material to Wikipedia, who in turn attribute the material to its authors.

Reverting
Edit histories make it simple to revert to a previous version if you disagree with an edit. But do this with caution, and be aware that there is a three revert rule. Many editors even abide by a one revert rule.

It's generally best to discuss any revert, either on the page's own talk page or on the user talk page of the user who made the edit in the first place.

Some experienced users are granted extra powers that enable them to revert even more easily. And some edits seem so obviously wrong that they are automatically reverted by software (which does make mistakes, but rarely, and these can themselves be easily reverted, it's all in the page history).

Blocks and bans
Particularly troublesome users can be blocked or banned from editing, either temporarily or permanently. These measures are not punishment, they are purely to protect Wikipedia and its other users.

Most users never even need to know about blocks and bans. Everyone makes mistakes and nearly all mistakes are honest, and you won't get blocked or banned for these. And if another user falsely threatens you with a block or a ban, that is itself disruption so it can easily boomerang on them.

Page protection
Some articles seem to be a magnet for unconstructive edits, and some pages are especially critical to the project.

So, in order to protect Wikipedia and minimise wasted time, editing these pages can be restricted.

There are various levels of protection. In the case of an article, any level of protection is a last resort, but it's sometimes for the best.

Oversight and deletion
Some material is especially damaging or dangerous or both, and is removed immediately and permanently, and (to all but a few especially trusted editors) completely. This is called oversight and is the responsibility of a very few, highly trusted contributors.

Less serious issues (copyright violations, for example) can be dealt with by any administrator, who can delete pages and their page histories, or just delete particular revisions of pages, removing them from public view. Deleting a particular version of an article, for example, is important if that version contains a copyright violation. All versions of an article can be reused, so any that violate copyright must be removed to ensure this.

But nearly all of the bad stuff that leaks into Wikipedia from time to time can be removed by any contributor, even an anonymous one, and they regularly and effectively do this. And we all thank you for this. Again, that's why Wikipedia works.