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Apple quietly adopts HTTP/2

Amongst all the new features in iOS 9, I spotted one on Twitter that I hadn’t seen before:

There is nothing cooler than seeing my iOS9 devices report HTTP/2 from Safari @ Welcome to the HTTP/2 future!

It turns out that Cory blogged about this several months ago, but otherwise this change seems to have passed very quietly.

The status quo – HTTP/1.1 – is over fifteen years old. The web has changed a lot since then, and decisions made for the web of 1997 just don’t make sense today. Enter HTTP/2: a new protocol intended to replace HTTP/1.1, with a design that’s appropriate for the modern web. It’s been in the works for several years, and was finally published as an RFC in May.

I first heard of HTTP/2 in Cory’s talk at PyCon, and I thought it was an interesting technical idea. He makes a compelling case for the benefits, but I didn’t expect it to be adopted quickly. Until lots of browers could use it, who would rush to adopt it server-side?

With iOS 9, that calculus has changed.

It turns out that Apple announced support for HTTP/2 all the way back in June, at WWDC: Networking with NSURLSession (start at the 13 minute mark). The same session introduced App Transport Security (HTTPS by default for all apps), and I suspect that overshadowed this announcement. It doesn’t help that I’ve found almost no mention of it in Apple’s developer docs.

But the crux is this:

As of iOS 9 and El Capitan, all NSURLSession requests can support HTTP/2. (And if you’ve been running the developer seeds, you’ve had it for a while.)

Apple have been using this themselves: remote access to HomeKit devices via iCloud all goes via HTTP/2. And I wouldn’t be surprised if they start using it to push out software updates, given that CDNs were explicitly called out as an HTTP/2 provider in that session.

Even assuming a very conservative adoption rate, there are now tens of millions of new clients that support HTTP/2. That’s got to push the needle on server-side adoption (and guess what I’m planning for next weekend!).

HTTP is a fundamental part of the web, and HTTP/2 is a key part of its future. I’m incredibly pleased to see Apple driving it forward.