TikTok for Developers is TikTok's platform of APIs and SDKs (software development kits) for apps and websites that connect to TikTok. Its products include Login Kit for sign-in, the Display API for reading profiles and videos, Share Kit and the Content Posting API for posting, and the Research API for researchers.
Login Kit is TikTok's implementation of OAuth 2.0, a standard that lets a user give an app limited access to an account without giving it the password. The developer registers the app to get a client key and secret, and requests scopes (named permissions). The user logs in on TikTok and consents; the app receives an authorization code and exchanges it on its server for an access token and a refresh token. With that token, the Display API's HTTP endpoints return the user's profile (/v2/user/info/) and the metadata of recent videos (/v2/video/list/). The scope user.info.stats adds like, follower, following and video counts. Scopes beyond basic profile data need approval from TikTok.
The APIs are run by TikTok; the developer documentation shows no price for them.