Tumblr allows users to post short blog entries and to follow and communicate with other members in a manner similar to a social-networking site. Accounts are free, with the site earning revenue through advertising, paid promotional posts and the sale of custom themes to users that change the visual style of their pages.
Tumblr differs from more standard blogs in that it limits the length of each post and focuses more on social-networking functions.
A user needs a valid email address to sign up for an account. She can then create a blog, which she interacts with through a dashboard. The dashboard allows users to create new posts, reblog the content of others, and "like" the posts of other users. Users can sync their blogs with Facebook and Twitter accounts for automatic update notifications.
Tumblr tends to allow more adult content to be displayed than other social-networking sites, such as Facebook. Users can share explicit photos and can embed sexually explicit videos that are hosted at other sites. These sites are usually flagged as "Not Safe For Work (NSFW)" and cannot be accessed unless a user is logged in to a Tumblr account. There is also a "safe mode" default setting for new Tumblr accounts that automatically restricts access to sites with adult content unless it is disabled by the user.