TikTok, also known in China as Douyin , is a short-form video hosting service owned by the Chinese company ByteDance. It hosts user-submitted videos, which can range in duration from 3 seconds to 10 minutes.

TikTok is an entirely separate, internationalized version of Douyin, which was released in the Chinese market in September 2016. It launched in 2017 for iOS and Android in most markets outside of mainland China; however, it became available worldwide only after merging with another Chinese social media service, Musical.ly, on 2 August 2018.

TikTok and Douyin have almost the same user interface but no access to each other's content. Their servers are each based in the market where the respective app is available. The two products are similar, but their features are not identical. Douyin includes an in-video search feature that can search by people's faces for more videos of them, along with other features such as buying, booking hotels, and making geo-tagged reviews.

Since their launches, TikTok and Douyin have gained global popularity. In October 2020, TikTok surpassed 2 billion mobile downloads worldwide. Morning Consult named TikTok the third-fastest growing brand of 2020, after Zoom and Peacock. Cloudflare ranked TikTok the most popular website of 2021, surpassing google.com.

Similar to Facebook and most other social media, TikTok has been subject to criticism over psychological effects such as addiction, as well as controversies regarding inappropriate content, misinformation, censorship, moderation, and user privacy.