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Rate Limit Rationale

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• 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 non-load-balanced services not served from the same network as public Q&A (chat, the API, etc.)
  • 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

Comments

• Voting & Flagging

  • Same amount of comment flags as one does post flags (default 10, may rise up to 100 based on flagging activity or reputation; see Flagging below)

    • Comment flag and post flag allowances are separate

  • 30 comment upvotes per day (automatic upvotes resulting from close votes do not count)

  • no minimum wait time between votes

    

  • Can only flag one comment every 5 seconds

• Deleting (treated like voting)

  • No limit per second (previous one-comment-per-5-second limit removed)
  • Can only delete own upvoted comments under 20 posts per day (multiple comments under same post are treated as one)
    • Despite what the message says, you can still delete an unlimited number of non-upvoted comments per day, even if you've hit the above rate limit.

• Creating

  • Three comments per 30 seconds

  

• Editing

  • comment can be edited every 5 seconds by its author or a diamond mod
  • comments cannot be edited after 5 minutes (except by diamond moderators)

Searching

• No rate limits for humans is what was stated, but testing has shown it to be 30 searches in 60 seconds (see comment on answer linked to).

  

• Anonymous users

  • are limited to a maximum of 500 results
  • can only search for three tags at a time (was previously limited to one tag, but later raised)
  • must solve a CAPTCHA unless they've already solved one in the last five minutes

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 IP address, they may not be limited.)

  

  • 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)

  • maximum of 6 questions per day
  • maximum of 50 questions per 30 days, on a rolling basis (50 questions in past 720 hours before current time).

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

• Stack Exchange staff members are not subject to these rate limits on meta sites

Answering

• Users with < 125 rep must wait 3 minutes between answers on most Stack Exchange sites, but must wait 30 minutes between answers on Stack Overflow. The longer wait time between answers on Stack Overflow was implemented as part of the response to a flood of ChatGPT 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

• Users of any reputation level can only answer the same question once every 60 seconds

• Users with the "staff" bit (i.e. Stack Exchange employees) are not subject to the above limits on meta sites

Accepting

• All must wait 15 minutes after asking to accept any answer

• All must wait 48 hours after asking to accept own answer

  

Editing

• Edit at most 10 of one's own posts per day (can be modified per site, but no site has modified it)

  • Additional edits to the same post aren't counted
  • Edits to posts created on the same or previous UTC calendar day don't count
  • Edits made to posts scoring -1 or lower don't count
  • Edits to deleted posts don't count
  • Once the limit is hit, no more edits can be made to any of one's own posts, even if the edit would be exempt per the above criteria
  • Does not apply to ♦ moderators, users with the moderator tools privilege ("10k+" users), or Stack Exchange staff members
  • Rollbacks aren't considered edits for any of the above checks

  You have already edited 10 of your own posts today; further edits are not allowed until tomorrow

  (Source: What exactly is the rate limit for editing your own posts?)

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

  • Limit is partially waived if submitting a tag wiki and excerpt suggested edit at the same time (which counts as two edits) - if the user only has space for one more pending edit, both edits will still be allowed, but they cannot submit another suggested edit until two of their pending edits are approved (i.e. they're no longer exceeding the limit)

• 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

• 10 flags per day by default

  • 1 bonus daily flag for every 10 net helpful flags in the user's flagging history (helpful minus declined, excluding other types such as disputed and aged away)
  • 1 bonus daily flag for every 2,000 reputation earned
  • A net negative helpful flag count can reduce a user's daily flag allowance to below 10
  • The number of daily flags is hard-capped at 100

• 5 seconds between flags (both flagging and retracting)

• 3 seconds between opening the flag dialog

  

  

  

• You can be banned from flagging when too many flags have been declined in a 7 day period; such a ban will automatically be lifted once the criteria no longer apply (after at most 7 days).

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)
• 80 reviews per First Questions queue per day if the queue size is 1000 or more on Stack Overflow
• Reviews on suggested edits to your own posts do count toward the limit if you haven't reached it yet, but will be allowed through even if you have.
• 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

• 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 (question-only votes can't be used once you've cast 25 votes on answers) (source)
  • To further elaborate: you get 10 Q-votes and 30 QA-votes per day. When you vote on a question, you'll use a Q-vote, and on an answer, you'll use a QA-vote. If you run out of Q-votes, you can continue voting on questions, but you'll be using QA-votes. However, once you have only 5 QA-votes left, you'll be blocked from using your Q-votes and all of your remaining voting for the day will use your QA-votes.
• 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, but if you now have more than 5 unused QA-votes, your Q-votes will be unblocked, allowing you to vote more times).
• If you vote and undo your vote 30 times, your vote gets 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

• once per second

Expanding revision history from user activity

• once per 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, 12 on Stack Apps, 24 on others. Source

Deleting

• Can only delete 5 of your own posts per day
  • Undeleting and re-deleting the same post on the same day won't count
  • Posts that were made on the same UTC calendar day or the previous UTC calendar day don't count
  • Posts that score -1 or lower don't count
  • Once the limit is reached, no more posts can be deleted, even if they'd be exempt per the above bullets
  • Doesn't apply to diamond moderators
• 5 delete votes (at 10k) with an extra delete vote for every 1k rep above 10k, max of 30, per day
  • When a 10k+ user with delete votes remaining deletes one of their own posts, that deletion will deduct 1 from their delete votes for the day.
  • Other than that, the counts between self-deleted posts and delete votes for others' posts are kept separate: the number of self-deleted posts is limited to 5 per the above criteria, and if you've used all your delete votes but have not hit the above limit, you can still delete your own posts up until the limit (the counter will show as negative).
• 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
• Can only cast one delete vote and one undelete vote on the same post, except when you are the post owner or a moderator.
  • If you previously deleted or undeleted someone else's post as a moderator, you cannot vote to delete or undelete the post again if you later cease to be a moderator.

Deleting/destroying accounts

• Moderators can delete/destroy only one account every 5 seconds.

Winter Bash hats

• Change hat once every 10 seconds

iOS and Android apps (deprecated)

• Due to depending on the API, one second between actions
  

• Unlike the normal API, which restricts users to 10,000 queries per day (see below), the iOS app is allowed a (theoretically) unlimited number of queries per day (restricted to 2^31 - 1 or 2,147,483,647, or the maximum number for a 32-bit signed integer). This does not apply to the Android app.

  • Note that this is likely to change given that app-specific API features are gradually being retired due to the discontinuation of the apps.

Stack Exchange API

• API request quotas
  • Request quotas are the maximum number of API requests in a rolling 24-hour period.
  • Maximum of 300 queries per 24 hours per IP address, if not using an API key value. Requests with an API key also count against this quota. It is not separate from the 10k quota, which means these 300 requests are likely to be consumed by applications using an API key.
  • Maximum of 10,000 queries per day per API key and IP address pair, if using a per-application API key, with some exceptions:
    • 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 100,000)
    • The above noted exemption for the iOS app, which has a special key that doesn't have daily API limits (see above section for more details)
    • The quota which is applied to the IP address is the same for all API requests made with a key value in the 24-hour period. The quota value which is used is the maximum quota assigned to any key which is used to make a request from that IP address within that 24 hour period (e.g., if a key with a 50k quota is used for a single request on the IP address, then all requests with a valid key value from that IP address in that 24 hour period have a 50k quota, regardless of what their normal quota would be).
  • Requests which use an access_token, in addition to a key, use a quota which is tied to the access_token. An access_token uniquely identifies an application + user pair. Each user has up to 5 additional 10,000 request quota pools which are allocated separately to the first 5 application + user pairs used for that user in a 24-hour period. Requests made with an access_token do not count against the IP based quotas.
• A hard limit of 30 requests from any IP address per second. SE considers "> 30 request/sec per IP to be very abusive and thus cut the requests off very harshly." In normal operation, requests will almost always be throttled in other ways well before that hard limit.
• 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 the overall load on SE's servers, and can change based on various other factors. The exact criteria used for issuing a backoff are not disclosed.
• SE uses multiple layers of rate limiting for the SE API. The criteria used for the rate limiting layers are not disclosed. Rate limiting is implemented both by the above mentioned backoff response and requests returning various errors, potentially with no additional information.