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HTTP/2 is based on Google’s SPDY protocol, which was developed to improve on page load latency and improve security over the existing HTTP 1.1 standard. Work on the new protocol began in 2012, with the first development version being a direct copy of SPDY. The finalized standard was published in May 2015, and on May of this year, Google announced that they would no longer support SPDY in Chrome.
How is HTTP/2 different from its predecessor? One major difference is that HTTP/2 is a binary protocol, not text-based. This allows it to be more compact, efficient to parse, and less prone to errors. One of the key advantages of the protocol is that it is multiplexed, meaning that multiple files can be transferred on a single connection. Another touted feature is Server Push, which allows the server to transfer resources to the client before they’re requested, pre-filling the cache.
Support for the new protocol is pretty good, including all the major browsers. Server-side, Apache2, Nginx and Microsoft IIS all support it, along with Node.js version 5.0 and above. Most of the browser vendors have stated that they will only be supporting HTTP/2 over TLS connections, although with the advent of Let’s Encrypt providing free SSL certificates, that’s an easy requirement to meet. According to figures collected by W3Techs in June of this year, around 8.4% of the top 10 million websites now support the new protocol. If you’re a Chrome user, you can use the HTTP/2 and SPDY indicator extension to tell you at a glance which of the sites you visit are served via HTTP/2.
So, when should you think about making the switch to HTTP/2? The answer is, it depends. Although browser support is very good, if your target audience is still stuck on older versions of IE then you’re out of luck, so do check your visitor stats to see if this is something that’s likely to benefit the majority of your users. What I take away from all this is that support and adoption of the new protocol are surprisingly far along and, as developers, this is a trend we cannot afford to ignore.
What sort of bundling strategy do you employ? Are you thinking of making the switch to HTTP/2, or maybe you already have? Let me know in the comments!