Liking another user's post on Tumblr publicly declares that you enjoyed or agree with the post, or that its content resonated with you in some way. While all individual Tumblr posts display all of the users who have liked it, most Tumblr themes don't display a complete list of all the posts an individual user has liked. If you want to see which posts another user has liked on Tumblr, you must use one of several other methods to view that information.
Some users install themes that display the most recent posts they've liked in a widget on their blogs' layouts. Depending on the theme the blog is using, this widget may display in the blog's footer, header or sidebar and is publicly visible to all visitors. Typically, a user can limit how many liked posts display in the widget, so that you'll be able to view only the last few posts the user has liked.
All Tumblr users can enable their primary accounts to share a syndicated list of posts they've liked from other users. To enable this feature, you must log into your Tumblr account, click the gear icon in your dashboard, and then click the "Dashboard" tab. Check the box next to "Share Posts I Like" and click the "Save" button to make your changes live. You can see the liked posts of any Tumblr user with this feature enabled by visiting the following URL, replacing "username" with the user's Tumblr username: http://www.tumblr.com/liked/by/username.
Viewing Individual Post Notes
You can see what users liked any Tumblr post by viewing its notes. To view the notes on a post in your dashboard, click the "Notes" link to display a scrolling pop-up box listing all the users who liked, replied to or reblogged the post. Tumblr denotes users who liked a post by listing "liked this" next to the their usernames. You can also view who liked an individual post by clicking the post's permalink in the blog and scrolling down to the notes section.
Limitations and Considerations
Because you can like posts only with your primary Tumblr account, the site doesn't enable the feature to share what posts you've liked for secondary blogs. You can make your liked posts private by visiting your blog settings, selecting the "Dashboard" tab and unchecking the box to share your liked posts. Click the "Save" button to immediately disable the feature. If a user has turned off sharing liked posts, you'll see a "Request Denied" error message page when you visit the liked-posts page for the user.
Many themes don't feature the option to display the user's liked posts. If so, and the user hasn't enabled sharing liked posts, you won't be able to view what posts the user likes unless you notice the username in the notes of an individual post.