Tumblr is a microblogging and social networking website founded by David Karp in 2007, and owned by Yahoo! since 2013. The service allows users to post multimedia and other content to a short-form blog. Users can follow other users' blogs. Bloggers can also make their blogs private. For bloggers, many of the website's features are accessed from a "dashboard" interface.
As of April 1, 2017, Tumblr hosts over 341.8 million blogs. As of January 2016, the website had 555 million monthly visitors.
Development of Tumblr began in 2006 during a two-week gap between contracts at David Karp's software consulting company, Davidville (housed at Karp's former internship with producer/incubator Fred Seibert's Frederator Studios which was located a block from Tumblr's current headquarters). Karp had been interested in tumblelogs (short-form blogs) for some time and was waiting for one of the established blogging platforms to introduce their own tumblelogging platform. As no one had done so after a year of waiting, Karp and developer Marco Arment began working on their own tumblelogging platform. Tumblr was launched in February 2007 and within two weeks, the service had gained 75,000 users. Arment left the company in September 2010 to focus on Instapaper.
In early June 2012, Tumblr featured its first major brand advertising campaign in conjunction with Adidas. Adidas launched an official soccer Tumblr blog and bought placements on the user dashboard. This launch was only two months after Tumblr announced it would be moving towards paid advertising on its site.
On May 20, 2013, it was announced that Yahoo! and Tumblr had reached an agreement for Yahoo! to acquire Tumblr for $1.1 billion in cash. Many of Tumblr's users were unhappy with the news, causing some to start a petition, achieving nearly 170,000 signatures. David Karp remained CEO and the deal was finalized on June 20, 2013.
With Tumblr's 2009 acquisition of Tumblerette, an iOS application created by Jeff Rock and Garrett Ross, the service launched its official iPhone app. The site became available to BlackBerry smartphones on April 17, 2010 via a Mobelux application in BlackBerry World. In June 2012, Tumblr released a new version of its iOS app, Tumblr 3.0 allowing support for Spotify, hi-res images and offline access. An app for Android is also available. A Windows Phone app was released on April 23, 2013. An app for Google Glass was released on May 16, 2013.
Tumblr blogs may optionally allow users to submit questions, either as themselves or anonymously, to the blog for a response. Tumblr also offered a "fan mail" function, allowing users to send messages to blogs that they follow.
On November 10, 2015, Tumblr introduced an integrated instant messaging function, allowing users to chat between other Tumblr users. The feature is being rolled out in a "viral" manner; it was initially made available to a group of 1500 users; other users may receive access to the messaging system if they are sent a message by any user that has received access to the system itself. The messaging system only supports text-based conversations, although other features (such as group chat and image embeds) will be added in the future. The messaging platform will also replace the fan mail system, which has been deprecated.
In May 2012, Tumblr launched Storyboard, a blog managed by an in-house editorial team which features stories and videos about noteworthy blogs and users on Tumblr. In April 2013, Storyboard was shut down.
An analysis by AddThis of shares through their service in 2011 noted that Tumblr sharing had increased by 1299.5%.
The service is most popular with the teen and college-aged user segments with half of Tumblr's visitor base being under the age of 25.
Tumblr is noted by technology journalists as having a sizable amount of pornographic content. The New York Times notes "pornography represents a fraction of content on the site, but not a trivial amount for a site with 100 million blogs." Karp revealed in June 2012 that between 2 and 4 percent of Tumblr's traffic is porn-related. However, an analysis conducted by news and technology site TechCrunch has shown that over 22% of all traffic in and out of Tumblr is classified as pornography. In addition, a reported 16.45% of blogs on Tumblr exclusively contain porn. Tumblr's Community Guidelines permits adult-oriented content but requires that blogs that contain occasional or substantial adult content to be flagged as such. Sexually explicit videos are not allowed to be uploaded to the website, but videos hosted elsewhere may be embedded. Some porn bloggers earn money by referring traffic to adult businesses through referrals and widgets.
As of July 20, 2013, policy updates enacted by Tumblr mean that pages classified as "NSFW" (not safe for work) will not feature in tag pages for users who are not logged in or who have the "Safe Mode" activated. For use