Tumblr is a microblogging and social networking website founded by David Karp in 2007 and currently owned by American company Automattic. The service allows users to post multimedia and other content to a short-form blog.

Microblogging is a form of blogging using short posts without titles known as microposts. Microblogs "allow users to exchange small elements of content such as short sentences, individual images, or video links", which may be the major reason for their popularity. Some popular social networks such as Twitter, Threads, Mastodon, Tumblr, Koo, and Instagram can be viewed as collections of microblogs.