Why have limits?

Limits alleviate some of the strain on the behind-the-scenes part of Twitter and reduce downtime and error pages. For the sake of reliability, Ywiotter have placed some limits, on the account actions, below:

Current Twitter limits

The current technical limits for accounts are:

• Direct Messages (daily): The limit is 1,000 messages sent per day.
• Tweets: 2,400 per day. The daily update limit is further broken down into smaller limits for semi-hourly intervals. Retweets are counted as Tweets.
• Threads.Tweet threads have a limit of 25 tweets - you have to then publish and then go into the last one to continue - and thus another 25.
• Changes to account email: 4 per hour.
• Following (daily): The technical follow limit is 400 per day. Please note that this is a technical account limit only, and there are additional rules prohibiting aggressive following behavior. 
• Following (account-based): Once an account is following 5,000 other accounts, additional follow attempts are limited by account-specific ratios. 

• Follow back limits - actually it changes over at 4548 or something close - from an upper limit of 5001 - to being 10% of people following you. They say it is more complex than this - it isn't. It is a straight sum. Take the number of people following you - work out 10% - round up to the next whole number and add that on - that is how many you can follow.

These limits include actions from all devices, including web, mobile, phone, API, etc. API requests from all third-party applications are tracked against the hourly API limit. People who use multiple third-party applications with their account will therefore reach the API limit more quickly. 

These limits may be temporarily reduced, during periods of heavy site usage. In such cases, Twitter will post an update on the Twitter status site.

Following:

Twitter does not limit the number of accounts that can be followed, overall but...

Every Twitter account is able to follow up to 400 accounts per day.

Verified Twitter accounts are able to follow up to 1,000 accounts per day.

In addition to the daily limits, there are follow ratios that go into effect, once you’re following a certain number of accounts: Every Twitter account can follow up to 5,000 accounts.

Once you reach that number, you may need to wait until your account has more followers before you can follow additional accounts.

This number is different for each account and is automatically calculated, based on your unique ratio of followers to following.

You may encounter a message that states, “You are unable to follow more people at this time.”

You’ll encounter this message for one of the following reasons:

• You’ve reached the daily follow limit.
• You can follow more accounts after a day has passed.
• You've followed too many accounts too quickly.
• Try again in an hour or so.
• You’ve hit a follow ratio limit.
• You can try again once your account has more followers, or you can unfollow a few accounts to follow new ones.
• Your account is locked or limited. Twitter may lock an account if appears to be compromised or if it is in violation of the Twitter Rules or Terms of Service, including due to aggressive follow behavior. Accounts in a locked state are limited in actions they can perform, including following. 

What happens if I hit a limit?

If you do reach a limit, Twitter will let you know, with an error message, telling you which limit you've hit. For limits that are time-based (like the Direct Messages, Tweets, changes to account email, and API request limits), you'll be able to try again after the time limit has elapsed.

The Tweet limit, of 2,400 updates per da,y is further broken down into semi-hourly intervals. If you hit your account update/Tweet limit, please try again in a few hours after the limit period has elapsed.