To approve or deny a follower request on the web: Sign in to your Twitter account.
Look for the follower request notification on the left side of your homepage.
Click the notification, and choose to either approve or deny the follower request. To approve or deny a follower request on an official app:
Twitter for Android: Under the Me tab, scroll towards the middle to find Follower Requests.
On the next screen you have the option to approve or deny individual requests or to accept all pending requests.

Android device:

Twitter for iPhone: Navigate to the Me tab. If you have any follower requests, you’ll see a banner under your Following and Follower counts that says Follower requests. Tap the banner.
You’ll see a list of all follower requests, and you have the option to approve or deny individual requests or to accept all pending requests.

iPhone:

Note: Approving follow requests can also be done on mobile.twitter.com.

If you don’t see a follower request notification on your homepage: You may have public Tweets. Protect your Tweets in order to control who follows you. You can do this in your account settings.
Users with public Tweets do not have the option to approve followers. If you previously had protected Tweets, any pending follower requests will not be accepted automatically. Those users will need to follow you again.
You may not have any follower requests. When there are zero requests, the notification message disappears completely from your homepage.
If you received an email notifying you of a new follower pending approval, but do not see that request in your pending requests, it’s likely that the user decided to cancel the request after sending it.

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