Tumblr has been growing bigger and bigger, but the type of things it's best at, small, media heavy posts, are now done, more and more, on mobile devices.
The new wave of mobile first or mobile only services, Instagram and friends, is the big threat, so Tumblr is treating mobile very seriously.
Earlier this year, the site rolled out a brand new mobile app, which was a huge upgrade over the existing one. Now it's doing the same for its mobile site.
The new default mobile theme is a noticeable improvement over the previous iterations, even though most of the changes are subtle.
For one, images now take up as much space as possible, a trend that most apps and mobile sites are following these days, an understandable one. The site is faster too since it's been redesigned from the ground up.
"The brand new mobile blog: completely redesigned for faster browsing, cleaner reading, and easier sharing. Like and reblog directly from index page; Share posts through Facebook, Twitter, or email; Built-in support for Pages; Full-width images and infinite scrolling," Tumblr succinctly listed