Privacy is one of the main concerns people talk about on the Internet. This is why internet companies have gone all the way to improve their privacy settings on the platform. This is why you see such options like limiting posts to certain friends or only to you on Facebook or making your account private on Instagram and Twitter.
Tumblr has decided to go the Instagram and Twitter route by allowing users to control if they want to show their Tumblr blog to the web. This is in the form of a toggle that is available on your dashboard which when turned on results in anyone that tries to view the post on your blog getting a missing page (404) error. However, the people that follow you will still be able to see your posts on their dashboard. Tumblr also says the toggle pairs with the block feature so in essence they are encouraging users to use the two features in tandem.
This new feature on Tumblr will join the other privacy related settings like the usual password, emailing important information about your Tumblr account and two-factor authentication which was added recently. You can also set your blog not to appear in search results which in conjunction with the block and hiding the blog from the web will make it easy for users to counter trolls.
To set up the new feature, login to your Tumblr, click the profile tab, click edit appearance, scroll down to directory and disable show this blog on the web.