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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

    Comment creation - You may add another comment in 24 seconds

  • 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; similarly, if the same user posts a question from a different site, they may not be limited.)

    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. Some of these per-site limits do also check the account, not just the IP address.
    • 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)

    Sorry, you are only allowed to ask 50 questions in a 30 day period

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. (Submitting a tag wiki edit along with a tag wiki excerpt edit at the same time for the same tag is not limited.)

* 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

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

Stack Exchange API

  • Maximum of 10,000 queries per day (per key and IP address if using a dedicated API key, or per IP address if not)

    • Some high-profile tools that actively help out with the Stack Exchange network receive special keys that grant them an extended limit (e.g. SmokeDetector has a limit of 20,000)
    • The above noted exemption for the mobile apps, which have special keys that don't have daily API limits (see above section for more details)
  • Maximum of one action-performing query per second

  • Occasionally, queries can return a backoff value, to indicate how much time a given application needs to wait before it can perform another query. This value depends on the number and speed of the queries and can change based on various other factors, and as such it's too complicated to fully list here.