HTTP/2, the second major version of Hypertext Transfer Protocol (HTTP) and the biggest update in years, has been finalized. While draft-17 has been anointed the proposed standard, it still has to get an RFC number, go through editing, and finally be published. Yet the real difference will only be seen when browser makers get on board.

On February 9, Google outlined its plans, namely adopting HTTP/2 in the coming weeks with Chrome 40. Today, Mozilla is joining the discussion by outlining its own roadmap for Firefox.

HTTP is an application protocol that forms the foundation of data communication for the World Wide Web. Over the years, it has become dated, and there have been many initiatives to speed it up. HTTP/2 will be the first new version of the HTTP protocol since HTTP 1.1, which was standardized back in June 1999.

Patrick McManus, network developer for Mozilla Firefox, says 9 percent of all Firefox release channel HTTP transactions are already happening over HTTP/2, although that’s not the latest draft-17 version. He outlined the current roadmap for HTTP/2 as follows:

  • The current Firefox 35 version uses a draft ID of h2-14 and uses it to negotiate with
  • Firefox 36, currently in beta, will support the official final “h2” protocol for negotiation next week. McManus said he expects “lots of new server side work to come on board rapidly now that the specification has stabilized.” Firefox 36 will also support draft IDs -14 and -15, and will use -15 to negotiate with Twitter as well as Google.
  • Firefox 37 and 38 have the same levels of support — adding draft-16 to the mix. The final h2 ALPN token will remain fixed. “These releases also have relevant Internet Engineering Task Force (IETF) drafts for opportunistic security over h2 via the Alternate-Service mechanism implemented,” McManus added.
  • Support for the various draft levels of HTTP/2 will be removed “sometime in the near future,” at which point Firefox will simply offer the “h2” of the proposed standard.

HTTP/2, currently being developed by the Hypertext Transfer Protocol Bis (httpbis) working group of IETF, is based on SPDY, a protocol developed primarily at Google to improve browsing by forcing SSL encryption for all sites and speeding up page loads. While various browser makers have used parts of SPDY, McManus said Firefox already sees more HTTP/2 connections made than SPDY ones.

McManus explained why this matters:

For both SPDY and HTTP/2 the killer feature is arbitrary multiplexing on a single well congestion controlled channel. It amazes me how important this is and how well it works. One great metric around that which I enjoy is the fraction of connections created that carry just a single HTTP transaction (and thus make that transaction bear all the overhead).

For HTTP/1 74 percent of our active connections carry just a single transaction — persistent connections just aren’t as helpful as we all want. But in HTTP/2 that number plummets to 25 percent. That’s a huge win for overhead reduction. Let’s build the web around that.

In short, it’s a very exciting time in browser land. Over the next few months we expect to hear a lot about HTTP/2 and how quickly it is being adopted.