The Wayback Machine - https://web.archive.org/web/20160617152108/https://dev.twitter.com/web/follow-button/web-intent

Follow Button Web Intent

Web Intents display Twitter actions optimized for display in a small browser window. A website may link to a follow Web Intent through a simple link on any website. Twitter’s JavaScript widgets use the follow Web Intent to prompt viewers to follow an account.

A follow Web Intent window features an inline login form for logged-out Twitter users.

Screenshot of a Twitter.com follow intent window displayed to a logged-out Twitter user

The user will follow the account on successful login through the inline follow web intent login form. The follow status is confirmed by the “Following” button displayed in the web intent window.

follow Web Intent logged in followed

We recommend rendering a Web Intent child window dimensions of at least 550 pixels wide and 420 pixels high.

Web Intent URL

https://twitter.com/intent/follow

Query parameters

A follow Web Intent must reference a Twitter account by screen_name or user_id. A screen_name may change; we recommend using user_id whenever possible.

screen_name required

The Twitter username of the account you would like the viewer to follow.

Example Value: twitterdev

user_id required

The Twitter user identifier of the account you would like the viewer to follow.

Example Value: 2244994945