Logging in is not required for viewing pages, and not even for editing them. However, it provides additional features, and in general projects recommend it.
Logging in 
Creating a user account means that you supply a username (your real name or a nickname) and a password. The system will reject a username that is already in use. A user account is created only once. You are then "logged in". Next time you log in you supply your username again and demonstrate with the password that you are the same person.
Edits you make are recorded under your username. If you are not logged in your edits are recorded under your IP address.
Logging in and setting preferences are currently done separately on each wiki. However, see Single signon transition.
Why log in? 
You don't have to log in to read any MediaWiki wiki. You don't even have to log in to edit a MediaWiki wiki – anyone can edit almost any page, even without logging in.
However, it's still a good idea to log in, for these reasons:
- Other users will be able to recognise you by your username when you make changes to pages. As a "name" an IP address is somewhat clumsy. Also, if you use computers at different locations (home, office, internet cafe, etc.) you have a different IP-address in each case; even in the same location, depending on the Internet connection, the IP-address may be different each time. Therefore a username is better to maintain an identity.
- You will have your own user page where you can write a bit about yourself, and a user talk page which you can use to communicate with other users.
- You will be able to mark an edit as minor, which avoids inconvenience for other users.
- You will be able to keep track of changes to modules you are interested in using a watch list.
- If you choose to give an email address, other users will be able to contact you by email. This feature is anonymous – the user who emails you will not know your email address. You don't have to give your email address if you don't want to.
- You will be able to rename pages.
- You will be able to set your own preferences, to change things such as:
- The number of pages displayed in Recent changes
- The fonts, colours and layout of the site, by using different skins.
How to log in 
Logging in and setting preferences are done separately on each wiki (for plans of changing this see Single login). You may find it convenient for yourself and useful for maintaining a cross-wiki identity to use the same username on each wiki that you use, if that name is still free.
First, make sure that your browser accepts cookies. Some browsers can accept or reject cookies from individual sites; users of these should configure the browser to accept cookies from each wiki you plan to edit, such as wikipedia.org.
Go to the wiki for which you want to log in. Click on the Log in link at the top right of the page. You will then be prompted to enter your username and password. If you haven't logged in before, you will need to enter your password twice.
You may give your email address if you like. Other users will be able to send email to the address, but they won't be able to find out what the address is.
If you click the box Remember my password across sessions, you will not have to give your password again when you access MediaWiki wiki from the same computer. This feature will only work if your password was not generated by the Mediawiki software. So change your password please.
Log in problems 
If you appear to be able to log in, but as soon as you try to look at a page after the 'Log in successful' page you appear logged out again, it is very likely to be a cookie problem. If you are certain that cookies are enabled, make sure that you haven't inadvertently listed the domain name of the wiki you are using (example: Wikipedia.org) on a list of sites to never allow cookies for (This feature is available in – at least – Mozilla Firebird 0.6 and above and Microsoft Internet Explorer version 6 and above). Also make sure your computer's date and time are set correctly; if they are not, cookies may expire before they are supposed to. In addition to these steps, check to make sure PHP's directory for storing session data is writable. This directory can be found in the php.ini file under the session.save_path setting.
If you log in and enabled the cookie feature, a subsequent log in as a different user without the cookie feature enabled will appear as logged out.
How to set preferences 
Click on the Preferences link at the top right of the page for various options, including:
- Changing your password.
- Changing the skin, which changes the way that the web pages look.
Your User page and User talk page 
As a logged in user, you will be able to create your own user page and user talk page. When you are logged in, you will see your username displayed at the top right of the page. Click on this to get to your user page, which you can edit in the same way as any MediaWiki wiki page.
Most users write a little bit about themselves and their interests on their user page.
You also have a User talk page. You can access this by clicking on the Talk link next to your username at the top right of the page. Other people may write messages in your user talk page by editing it, and you can respond. See MediaWiki User's Guide: Talk pages for more..
How to log out 
You can log out any time by clicking on the Log out link at the top right of the page.
How to force logging in for editing 
This is controlled through a wg variable.
how to force logging in for viewing 
This is controlled through a wg variable.
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