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I noticed that I can only perform certain actions such as commenting a finite number of times in a given period of time. Obviously, rate limiting is in place to prevent accidental misuse or intentional abuse of certain features.

Where else is rate limiting applied on Stack Exchange sites, and what are the limits?

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280

Rate Limit Rationale

Loading pages

  • Undisclosed limit, applies to IP addresses
    • Applies to the entire network; if one makes too many requests on one or more sites, access to all network sites is restricted
    • Does not apply to chat sites
    • Should not be triggered during normal browsing; if you get it, it either means you're sharing your IP with multiple users accessing the network, or your browser or an extension is hitting the site with one or more extra requests every time you load a page

Too many requests: This IP address has performed an unusual high number of requests and has been temporarily rate limited.

Comments

  • Voting & Flagging

  • Deleting (treated like voting)

    • No limit per second (previous one-comment-per-5-second limit removed)
    • Can only delete own comments under 20 posts per day (multiple comments under same post are treated as one): enter image description here
  • Creating

  • Editing

    • comment can be edited every 5 seconds by its author or a diamond mod Comment editing - You may only edit a comment every 5 seconds
    • comments cannot be edited after 5 minutes (except by diamond moderators)

Searching

Asking

  • Users with < 125 rep on the current site, 40 minutes since their last question anywhere on the network (This applies to the user's IP address, not their account. If the user shares that IP with other users, they can be limited by the other user asking a question anywhere on the network.)

    Question limit - You can only post once every 40 minutes

    • Other per-site limits may apply; e.g. on Stack Overflow, new users can only ask once every 90 minutes
    • While the limit is waived for users with 125+ reputation on a given site, questions posted on sites where one has 125+ reputation still count toward the rate limit for sites where one doesn't. For instance, if you ask a question on a site where you have 150 rep, you can't ask another question on a site where you have only 100 rep for the next 40 minutes; however, you can ask them in reverse order immediately (first on the 100-rep site, then on the 150-rep site).
  • Users limited by Anti-Recidivism System, one question per week

  • Users limited from asking questions for 1 – 7 days based on the performance of their previous questions
  • Users prevented from asking questions due to the quality filter: one question per 6 months
  • Users with < 10k rep trip CAPTCHA* if more than once per 60 seconds, or within 5 seconds of starting new post
  • Users with ≥ 10k rep trip CAPTCHA* if more than once per 30 seconds, or within 5 seconds of starting new post
  • On Stack Overflow, Super User, Server Fault and Mathematics (not active on all other sites)

Answering

  • Users with < 125 rep must wait 3 minutes between answers
  • Users with between 125 and 10k rep trip CAPTCHA* if more than once per 60 seconds, or within 5 seconds of starting new post
  • Users with ≥ 10k rep trip CAPTCHA* if more than once per 30 seconds, or within 5 seconds of starting new post

  • Maximum of 30000 characters for the Markdown source of answer.

    Answer Character Limit

Accepting

Editing

  • edit at most 5 of one's own posts per day, more for high-rep users (scales with reputation), does not apply to ♦ mods (multiple edits of same post are fine)

    You have already edited 5 of your own posts today; further edits are not allowed until tomorrow

  • At most 5 pending suggested edits per editor (20 on beta sites)

  • Unregistered users can't suggest edits on posts < 10 minutes old
  • Users with < 10k rep trip CAPTCHA* if more than once per 30 seconds, or faster than 5 seconds after starting edit
  • Users with ≥ 10k rep trip CAPTCHA* if more than once per 10 seconds, or faster than 5 seconds after starting edit
  • You can only save a tag wiki edit once every 30 seconds, or once every 10 seconds if you have enough reputation (20k/4k on beta sites) to bypass the review queue.

* For all of the above thresholds for hitting CAPTCHA, if you have at least 200 reputation and have solved a CAPTCHA in the last 5 minutes, you will not have to solve one again.

Flagging

Reviewing

  • 20 reviews per queue per day if the queue size is less than 1000 (150 on Stack Overflow)
  • 40 reviews per queue per day if the queue size is 1000 or more (150 on Stack Overflow)
  • No review limit for ♦ mods

    Thank you for reviewing 20 Close Votes today; come back tomorrow to continue reviewing.

Chat

  • 1 second between two messages, here's the true throttle curve

    Chat Throttle Curve

  • There is a similar throttle for starring (details unknown)

  • There is a similar throttle for searching (details unknown)
  • Star limit is 20 stars per room, per day for each user.
  • 30 seconds between creating chat bookmarks

Voting

  • 30 votes per day +10 for questions only (Q only votes can't be used after 25 votes cast on answers. Source)
  • If one of the posts you vote on gets deleted the same day as you vote, your limit is recalculated as if you never cast that vote (i.e. in most cases, you can cast one more vote in this case).
  • If you vote and undo your vote 30 times, your vote gets locked in.

    Your vote is now locked in

Logging in

  • 3 failed attempts within a minute before a CAPTCHA is displayed

Changing usernames

  • Last username change must be less than 15 minutes or more than 30 days ago. Does not apply to ♦ mods or accounts that are less than 2 days old.

Showing Upvote/Downvote totals

enter image description here

Expanding revision history from user activity

  • once per second

    You may only load 1 revision every second

Closing

  • Can open close dialog once per 3 seconds
  • 50 close/reopen votes/day/user on Stack Overflow, Mathematics, Server Fault, Super User and Ask Ubuntu, 24 on others. Source

    Close Dialog rate limit box

Deleting

  • 5 of a user's own posts can be deleted by them per day
  • 5 delete votes (at 10k) with an extra delete vote for every 1k rep above 10k, max of 30, per day
  • Question must be closed in order to be able to vote to delete it
  • A question can't be voted to delete until 2 days after closure, unless 20k+ and question score -3 or lower

Destroying accounts

  • Moderators can destroy only one account every 5 seconds.

Winter Bash hats

  • Change hat once every 10 seconds

iOS and Android apps

  • Due to depending on the API, one second between actions
  • 2
    How are rate limits for non-humans implemented? Is a count of searches within a short period of time (lets say 5 seconds) calculated each time someone does a search? – user784637 Feb 19 '13 at 8:41
  • 17
    Why are there even limits on the diamond mods? – Undo - Reinstate Monica May 31 '13 at 15:52
  • @LanceRoberts What does "timer resets" mean, Sir? – Ave Maleficum Mar 9 '14 at 13:08
  • 2
    @AveMaleficum, when you vote on a comment, a timer starts. Everytime you click on the vote or flag button instead of having a smaller amount of time left, the timer resets itself. So you end up trying to time things in your head waiting for it to expire, see here. – Lance Roberts Mar 9 '14 at 16:00
  • 1
    There's also a limit for page requests per IP address per time period which I think must have recently been tightened (saw it twice yesterday) but I don't know what the exact limit is. – Martin Smith Mar 9 '14 at 17:44
  • Shouldn't per IP throttling occur only for anonymous users? IMO all API calls within the page should have a token associated with them and be throttled per user. – paulkon Mar 20 '14 at 17:21
  • What is the point of throttling per action with respect to DoS as opposed to global rate-limiting? – paulkon Mar 20 '14 at 17:36
  • 6
    ...yay, another 1 secondS. Why is it so hard to not fix all of these once and for all? – Werner Mar 30 '14 at 14:08
  • @Werner You linked to the tweet that answers your question. – michaelb958--Reinstate Monica Mar 30 '14 at 21:07
  • 2
    @michaelb958: Sadly it doesn't answer it. It just gives Jeff's opinion about these things. There are so many quantifiers on this website and I wonder why nobody ever takes to time to consider the singular/plural issue from the start... It seems as simple as writing a function where you pass it the quantity and it will return either an "s" or nothing and append that to the quantifier. It seems so fundamentally straight-forward. – Werner Mar 31 '14 at 0:58
  • 2
    @Werner Jeff was the original CTO, and the pluralisation code was written under his watch (if not by him), so his opinion carries a little more weight. The current team could fix them now if it justified the resources, and if they weren't scared of the giant S. (They might be fixing them right now, and they just haven't told us yet so Jeff doesn't find out until that security upgrade's done.) – michaelb958--Reinstate Monica Mar 31 '14 at 1:10
  • 3
    @LanceRoberts How should the chat throttle chart be interpreted? What's the data used to generate it? – Stijn Jul 28 '14 at 9:27
  • @Shadow, any reference on the comment rate-limit changes? – Lance Roberts Mar 11 '15 at 14:24
  • @Lance trial and error following this bug report - asked the dev for confirmation. – Shadow The Princess Wizard Mar 11 '15 at 15:01
  • @Werner, perhaps they should use MediaWiki's jquery.i18n. – Nemo Apr 29 '15 at 9:17

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