In most cases, a post which is "locked" cannot be modified in any way. Locking prevents...
- ...voting on the post (including close/reopen votes for questions)
- ...answering (for questions)
- ...flagging (though "in need of moderator intervention" flags are still allowed, except in the case of Historical Significance locks - see below)
The one exception to this is the "Comments only lock", which only prevents new comments from being added to the question or answer that is locked.
Who can lock a post?
Site moderators can apply specific types of locks to questions and answers.
Also, the system itself will lock posts in certain situations:
- if the post is deleted via "spam" or "abusive" flags.
- if the post is migrated to another site.
- if the post was migrated to the current site, and then rejected.
- if a question was merged into another question, the answers will be moved and the source question will be locked.
How long do posts stay locked?
This depends on why it was locked to begin with.
- When a moderator locks a post they're required to select how long the lock should remain in place. The options are: 1 hour, 1 day, 1 week, permanent. At the end of this time, the system will automatically unlock it.
- When the system locks a post it stays locked indefinitely - only a moderator can unlock it.
A moderator can manually unlock a locked post at any time if they deem it necessary.
When should a post be locked?
As a general rule, temporary locks should be used whenever modifications to a post are causing serious problems on the site. For example:
- Edit wars
- Extended bickering in comments (but see: a guide to moderating comments)
- A controversial post that is under discussion on meta
Permanent locks should almost never be used, with the exception of those imposed by the system itself. There are two exceptions:
An extremely popular question which is now considered inappropriate for the site may be locked for "Historical Significance": this alters the appearance of the question, automatically locks all answers as well, and disables flagging completely. This lock should be reserved for cases where a cherished cultural artifact would otherwise be deleted; do not use it for any other purpose.
A "wiki" is a question whose answers can be edited by low-reputation users, attributed to multiple authors, and do not grant reputation to the original author. They're occasionally useful in cases where information must be compiled by multiple authors (for example, a list of resources or documentation for the site itself); in these cases, locking the question both prevents it from being closed and prevents further answers from being added.
- What is a "locked" post? on Meta Stack Exchange
- What is a historical lock, and what is it used for? on Meta Stack Exchange
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