Blockstack is a network for Decentralized application on top of a blockchain network.  Blockstack aims to address the centralization at the application-layer of the internet. More specifically, Blockstack builds an alternate DNS and alternate public-key infrastructure . It's the first implementation of a decentralized DNS system on top of the Bitcoin blockchain .  It combines DNS functionality with public key infrastructure and is primarily meant to be used by new blockchain applications. Blockstack is being developed by a group of engineers and researchers coming from both industry and academia  and is released as open-source. Other systems like Namecoin have implemented decentralized DNS using blockchains earlier by using blockchains other than Bitcoin. Blockstack became operational on the Bitcoin blockchain in September 2015.  As of March 2016, Blockstack was the largest non-financial system using the Bitcoin blockchain by transaction volume.
Blockstack Public Benefit Corporation
Founded in 2013 as Onename , Blockstack raised $5.45 million venture capital from a number of major players, including Union Square Ventures , AngelList founder Naval Ravikant , and Digital Currency Group . 
In May 2017, at CoinDesk 's "Consensus 2017" blockchain conference in New York, Blockstack released a decentralized browser add-on ,  described as "a kind of Netscape for the decentralized internet, running apps on a plethora of blockchains".  The purpose of this add-on is to allow developers to use Blockstack's tools (decentralized identity, storage, and payments) to "create consumer-facing apps ". The add-on works with any browser, including Chrome , Safari , and Firefox .