Tumblr is shedding its identity as a desktop-only blogging platform and expanding its mobile presence this month at a breakneck pace.

Monday brought promoted posts to Tumblr's apps, Tuesday saw the debut of a Windows Phone 8 app, and Wednesday delivered a refreshed iOS app with a slew of new features. The app was once just a mobile extension of the Tumblr website, focused largely on writing blogs and reblogging content.

Tumblr is going social with the latest version of its iOS app. Now you can share posts on Facebook and Twitter or email them to friends, taking content outside the realm of Tumblr and onto other networks.

Tumblr is also making it easier to save content with Instapaper and Pocket reader integration.

I probably wouldn't pen a lengthy blog post within the app, but the sharing and saving features make Tumblr's iOS app a viable alternative to using the platform on a desktop.

Hands on with the iOS app

I downloaded the upgraded app on an iPhone 4S, and it looks similar to the prior version. After testing the Windows Phone 8 Tumblr app on Tuesday, I prefer Tumblr's use of Microsoft's style guidelines for headings and the appeal of seeing images on the WP8's home and lock screens. Otherwise, the WP8 and iOS apps released this week look and feel similar.

Tumblr also added an essential feature from its website to the iOS app: the ability to view animated GIFs. GIFs are huge draws on Tumblr--sometimes it feels like GIFs comprise the bulk of the site's content--and now you can see them in their full, animated glory as you scroll down on an iPhone or iPad.

So which Tumblr app rules them all?

The iOS version has great functionality, but the WP8 app is a bit more stylish. The recently redesigned Android app is perhaps the most appealing, with a cascading row of round icons that appear when you tap to post.

See also:

No more smiley faces in Apple's App Store for developers

Tumblr ads go mobile

Hands on with the new Yahoo app for iPhone