Verizon Communications Inc. has agreed to sell its blogging website Tumblr to the owner of popular online-publishing tool WordPress.com, unloading for a nominal amount a site that once fetched a purchase price of more than $1 billion.

Automattic Inc. will buy Tumblr for an undisclosed sum and take on about 200 staffers, the companies said. Tumblr is a free service that hosts millions of blogs where users can upload photos, music and art, but it has been dwarfed by Facebook, Reddit and other services.

Verizon...