Tumblr is a blogging/microblogging platform with a focus on data sharing between individual blogs. Users can create and disseminate data in a visual or HTML editor, using standard Tumblr posting formats: text, photo, quote, link, chat, audio, and video.

Built-in customization tools allow users to manipulate the appearance of their blog with little knowledge of web development. Tumblr also provides a CSS/HTML customization panel for more advanced users, including theme documentation and the ability to upload/alter theme asset files (e.g., CSS, JS).