Tumblr today introduced a feature that lets you hide your blog from the web so its content can only be viewed on Tumblr.com and in its native apps for mobile devices. The move, which Tumblr positioned as a privacy measure, will "let you better control who gets to see your stuff and who doesn't," the company said in a blog post. Once you set your blog to not be shown on the web, anyone who visits its URL will see a 404 error. But anyone who follows your blog will be able to see it on their dashboard when they log into Tumblr, either on the web or in its apps.

Tumblr says the toggle "pairs nicely with the block feature." The idea behind both features, the company says, is to make it easier to hide posts from the public, particularly trolls and abusers. But Tumblr's privacy features remain generally confusing. You still can't make your primary blog private, but you can set up a secondary blog protected by a password. Password-protected blogs feel like something out of another era — Instagram and Twitter are among the social networks that have long let you make your account private and then whitelist your followers, making it easier to keep trolls out.

The secondary effect of Tumblr's move today is to make it less of a web company and more of a walled garden. I don't imagine Tumblr users will hide their blogs from the web en masse — though creators of Tumblr's many famous porn blogs might! But driving users to Tumblr.com and apps makes it easier to deliver targeted advertising to them, and I wonder if that isn't part of Tumblr's calculation in making such a move. I also question the decision to present visitors to private blogs with a 404 page, which implies the blog has been deleted. In a year that has been very bad to the web, Tumblr just made it a little more broken.