Originally answered on Quora
Change your password
If you’ve connected third-party tools which are following and unfollowing for you the easiest way of removing them is to change your password.
As they have access to your Twitter account as you’ve given them permissions, changing your password means these automatic following apps won’t be able to take action on your behalf.
To change your password:
- Go into your settings
- Fill out the form
- Log out of Twitter
2. Type in your username/account info
3. Tick the box and have the email sent to your inbox
4. As of November 2019, the email looks like this
5. Press the button (or copy the link and paste it into your browser- some emails don’t allow clickable links in the spam).
6. Change your password
You can also revoke access
If you’ve connected third-party tools to follow people to your account you can stop those tools individually. This can be useful if you have multiple tools connected to Twitter and don’t want to reset all of them.
You can then click on the app you wish to revoke and revoke its access.
If you’re concerned about the fraudulent use of third-party tools on your account then always change your password.
If you try and do this on Instagram and they pick up on you using these services you’re made to change your password.
See Twitter’s Offical Help on the topic: About third-party apps and log in sessions