While many Tumblr users use their blogs as a space for self-expression meant to be shared with friends, other Tumblr users and the public at large, some users may not always feel comfortable expressing themselves in such a public manner. To address this concern, Tumblr offers a private post feature, though it handles private posts differently depending on the type of blog the post is on.

Private Posts vs. Private Blogs

Tumblr distinguishes between private posts and private blogs. All blogs run by a single user are managed under one email address. The first blog you set up under an email address is the primary blog. This blog cannot be wholly private, but it can contain private posts. However, you can mark secondary blogs as private by password-protecting them so that only those with the correct password can access them. Secondary blogs can also have multiple members, even when private, while primary blogs can only have one.

Protected Content

Posts on a password-protected blog allow you to post content you may not be comfortable with releasing to the general Internet-using public. For instance, writers or artists might use a private blog to present early versions of their work to a few critique partners or interested friends. Parents may also use protected blogs as a way to show off pictures of their family in a central space, without publicly posting pictures of their children.

Safe Spaces

Tumblr is an intersection of a lot of subcultures and minority groups; while conversations on topics relevant to these groups do take place in public posts, having public posts invites outsider commentary, and can lead to hate and trolling on sensitive posts. Private posts on group blogs allow members to have a safe space where they are free to express their thoughts and issues, without allowing outsiders to engage in shaming and other oppressive behavior.

Journaling

You can create private posts in your primary or secondary blog as a method of journaling. Such an online journal allows you to maintain an archive of posts for later review, without the potential of losing content due to a computer crash or other catastrophe. Tumblr's tagging system also makes it easy to review all posts you make on a single topic or event.