Tumblr uses a heart symbol to indicate that a user has liked a post.
Clicking the heart records the user’s approval or appreciation and adds the post to that user’s Likes, subject to Tumblr’s account and privacy settings. The heart is also visible in the post’s notes, where users can see engagement from other Tumblr accounts.
Tumblr’s heart is distinct from the reblog icon. A like generally saves or acknowledges a post without publishing it to the user’s own blog, while a reblog republishes the content to that blog and can add commentary. Both actions are central parts of Tumblr’s interaction system.
The heart symbol is common across modern social platforms, so it is sometimes mistaken for a Tumblr-specific invention. Tumblr helped popularize a broader style of lightweight, visual interaction alongside reblogging, tagging, following, and dashboard-based browsing. Likes may be used simply to bookmark content, not only to express strong approval.