If you only read the Wikimedia project websites, no more information is collected than is typically collected in server logs by web sites in general.
If you contribute to the Wikimedia projects, you are publishing every word you post publicly. If you write something, assume that it will be retained forever. This includes articles, user pages and talk pages. Some limited exceptions are described below.
Publishing on the wiki and public data 
Simply visiting the web site does not expose your identity publicly (but see private logging below).
When you edit any page in the wiki, you are publishing a document. This is a public act, and you are identified publicly with that edit as its author.
When you publish a page in the wiki, you may be logged in or not.
If you are logged in, you will be identified by your user name. This may be your real name if you so choose, or you may choose to publish under a pseudonym, whatever user name you selected when you created your account.
If you have not logged in, you will be identified by your network IP address. This is a series of four numbers which identifies the Internet address from which you are contacting the wiki. Depending on your connection, this number may be traceable only to a large Internet service provider, or specifically to your school, place of business, or home. It may be possible that the origin of this IP address could be used in conjunction with any interests you express implicitly or explicitly by editing articles to identify you even by private individuals.
It may be either difficult or easy for a motivated individual to connect your network IP address with your real-life identity. Therefore if you are very concerned about privacy, you may wish to log in and publish under a pseudonym.
When using a pseudonym, your IP address will not be available to the public except in cases of abuse, including vandalism of a wiki page by you or by another user with the same IP address. In all cases, your IP address will be stored on the wiki servers and can be seen by Wikimedia's server administrators and by users who have been granted "CheckUser" access. Your IP address, and its connection to any usernames that share it may be released under certain circumstances (see below).
If you use a company mail server from home or telecommute and use a DSL or cable Internet connection, it is likely to be very easy for your employer to identify your IP address and find all of your IP based Wikimedia project contributions. Using a user name is a better way of preserving your privacy in this situation. However, remember to log out or disconnect yourself after each session using a pseudonym on a shared computer, to avoid allowing others to use your identity.
The wiki will set a temporary session cookie (*wiki*_session) whenever you edit a page of the site. If you do not intend to ever log in, you may deny this cookie, but you cannot log in without it. You may also need it in order to pass a captcha test. It will be deleted when you close your browser session.
More cookies are set when you log in, to avoid typing in your user name (or optionally password) on your next visit. These last up to 30 days. You may clear these cookies after use if you are using a public machine and don't wish to expose your username to future users of the machine. (If so, clear the browser cache as well).
Many aspects of the Wikimedia projects' community interactions depend on the reputation and respect that is built up through a history of valued contributions. User passwords are the only guarantee of the integrity of a user's edit history. All users are encouraged to select strong passwords and to never share them. No one shall knowingly expose the password of another user to public release either directly or indirectly.
Private logging 
Every time you visit a web page, you send a lot of information to the web server. Wikimedia doesn't analyse or store this information, primarily due to perfomance reasons.
However, when you use a pseudonym, your IP address will be stored on the database. IP addresses of users are frequently used to correlate usernames and network addresses of edits in investigating abuse of the wiki, including the suspected use of malicious "sockpuppets" (duplicate accounts), vandalism, harassment of other users, or disruption of the wiki. This info is normally discarded after about one week.
Developers may do extra logging in the course of solving technical problems, in tracking down badly-behaved web spiders that overwhelm the site and investigating abuse of the wiki.
Policy on release of data derived from IP logs 
It is the policy of Wikimedia that personally identifiable data collected in server logs, or through records in the database via the CheckUser feature, may be released by the system administrators or users with CheckUser access, in the following situations:
- In response to a valid subpoena or other compulsory request from law enforcement
- With permission of the affected user
- To the chair of Wikimedia Foundation, his legal counsel, or his designee, when necessary for investigation of abuse complaints.
- Where the information pertains to page views generated by a spider or bot and its dissemination is necessary to illustrate or resolve technical issues.
- Where the user has been vandalising articles or persistently behaving in a disruptive way, data may be released to assist in the targeting of IP blocks, or to assist in the formulation of a complaint to relevant Internet Service Providers
- Where it is reasonably necessary to protect the rights, property or safety of the Wikimedia Foundation, its users or the public.
Wikimedia policy does not permit public distribution of such information under any circumstances, except as described above.
Sharing information with third parties 
Except where otherwise specified, all text added to Wikimedia projects is available for reuse under the terms of the GFDL, except for Wikinews, where the text is available under a Creative Commons Attribution License.
Wikimedia will not sell or share private information, such as email addresses, with third parties, unless you agree to release this information, or it is required by law to release the information.
Security of information 
The Wikimedia Foundation makes no guarantee against unauthorized access to any information you provide. This information may be available to anyone with access to the servers. A partial list of those people can be found in the developers list.
E-mail, mailing lists and IRC 
You may provide your e-mail address in your Preferences and enable other logged-in users to send email to you through the wiki. Your address will not be revealed to them unless you respond, or the email bounces. The email address might be used by the Wikimedia Foundation to communicate with users on a wider scale.
If you do not provide an email address, you will not be able to reset your password if you forget it. However, you may contact one of the Wikimedia server administrators to enter a new mail address in your preferences.
You can remove your email address from your preferences at any time to prevent it being used.
Mailing lists 
If you subscribe to one of the project mailing lists, your address will be exposed to any other subscriber. The list archives of most of Wikimedia's mailing lists are public, and your address may find itself quoted in messages. The list archives are also archived by Gmane and other services. Mails are usually not deleted or modified, but it may be done in extreme cases.
Information email addresses 
Some email addresses (see below) may forward mail to a team of volunteers trusted by the Foundation to use a ticket system such as OTRS to view them and answer them. Mail sent to the system is not publicly visible, but is visible to this group of Wikimedia volunteers. By sending a mail to one of these addresses, your address may become public within this group. The ticket system team may discuss the contents of your mail with other contributors in order to best answer your query.
Addresses that direct to the ticket system system include:
- info-de AT wikipedia DOT org
- info-en AT wikipedia DOT org
- info-es AT wikipedia DOT org
- info-fr AT wikipedia DOT org
- info-it AT wikipedia DOT org
- info-nl AT wikipedia DOT org
- info-pl AT wikipedia DOT org
IRC channels are not officially part of Wikimedia proper. By participating in an IRC channel, your IP address may be exposed to other participants. Different channels have different policies on whether logs may be published.
User data 
Data on users, such as the times at which they edited and the number of edits they have made are publicly available via "user contributions" lists, and in aggregated forms published by other users.
Removal of user accounts 
Once created, accounts of users which contributed to the project will not be removed. It may be possible for a username to be changed (depending on the policies of your local wiki and on the number of edits you have). The Wikimedia Foundation does not guarantee that a name will be changed on request.
Whether specific user information is deleted is dependant on the deletion policies of the project that contains the information.
Deletion of content 
Removing text from Wikimedia projects does not permanently delete it. In normal articles, anyone can look at a previous version and see what was there. If an article is "deleted", any user with "administrator" access on the wiki, meaning almost anyone trusted not to abuse the deletion capability, can see what was deleted. Information can be permanently deleted by those people with access to the servers, but there is no guarantee this will happen except in response to legal action.