Administrators have the ability to block users and IP addresses. Blocked users and IPs cannot edit pages, while they remain able to read pages and look at their source code.
 Block reasons
Users and IP addresses may be blocked for a variety of reasons, including and not limited to:
- Edits clearly made in bad faith
- Blanking pages or parts of pages
- Creation of spam pages
- Repeated policy violations
- Constantly remaking a deleted page
- Overtly negative attitude towards other users
- Evasion of existing block
 Block warnings
For policy violations or disruptiveness, users should be warned by an admin before a block is made. Non-admins can point out that a user is violating a policy or being disruptive, but generally only admins should use language that implies a block is imminent.
If a user continues to do something for which they've been blocked before, a warning is less useful.
For obvious spam or vandalism, warnings are generally fruitless, and indeed discouraged. Excessively blatant violations may also deserve unwarned blocks.
 Block lengths
Generally, the length of a block is at the complete discretion of the administrator giving it; there are no hard-and-fast rules about how long blocks should be for specific offenses.
- Short blocks range from 1 day to a week; 3 days is a common short block length. Short blocks are generally given for minor or first-time offenses.
- Medium blocks range from a week to a month or two. These tend to be given for severe first-time offenses or multiple offenses.
- Long blocks range from a few months to a year. These are generally reserved for users with useful contributions but a colourful block history, or severe offenses that do not warrant an infinite block.
- Indefinite blocks (more commonly known as infinite blocks and permabans) are used in cases where a user has been deemed "a lost cause", with no chance of being a useful contributor in the future. This generally results from repeated blatant disregard for policy. Infinite blocks also apply to vandal-only and spam-only accounts as well as malicious sockpuppets.
As IP addresses may change over time, long blocks should be applied to them very frugally and only when absolutely necessary. IPs should never be infinitely blocked.
 Block explanations
Admins are encouraged to explain the reason for a block on the user's talk page, especially if the reason cannot be adequately explained in the reason box when the block is given. This should generally be done by the admin who gave the block, not someone else.
 Block appealing
Historically, it is rare for a user to appeal a block. Should a user wish to do so, they should do so on their talk page, as this is the only page a blocked user can edit. Block-appealing users should make an effort to remain civil; angrily complaining about a block may simply result in having the block extended, or losing the privilege of editing one's own talk page for the duration of the block.
Discussion of a block should generally be limited to the user in question, the administrator who applied the block, other administrators, and possibly other users who were involved in the situation (e.g. the user who was personally attacked).
It is possible to become unintentionally blocked due to inheriting the IP of a blocked user. Should this occur, one should post on their talk page or e-mail an admin their username, the block ID, and their IP.
Note that users with a history of being disruptive may lose the privilege of editing their own talk page and/or using the wiki's email function immediately upon being blocked. A user may also lose the privilege to edit their talk page during a block if they were blocked for behavior on their talk page.
 Range blocks
A range block is a wiki feature which allows simultaneous blocking of a chunk of similar IP addresses. Range blocks are to be used sparingly, when a troublesome user is constantly coming back with a new IP address within a relatively narrow range, and should generally be restricted in length just like individual IP blocks.
 Related pages
- IP Block List - lists currently blocked addresses and usernames.
- Block log - shows all blocks and unblocks.
- Special:Blockip - use this to block or unblock a user (admins only)
- MediaWiki:Blockedtext - the text a blocked user sees when they try to edit a page.