The state and rate of HTTP/2 adoption

http2 logoThe protocol HTTP/2 as defined in the draft-17 was approved by the IESG and is being implemented and deployed widely on the Internet today, even before it has turned up as an actual RFC. Back in February, already upwards 5% or maybe even more of the web traffic was using HTTP/2.

My prediction: We’ll see >10% usage by the end of the year, possibly as much as 20-30% a little depending on how fast some of the major and most popular platforms will switch (Facebook, Instagram, Tumblr, Yahoo and others). In 2016 we might see HTTP/2 serve a majority of all HTTP requests – done by browsers at least.

Counted how? Yeah the second I mention a rate I know you guys will start throwing me hard questions like exactly what do I mean. What is Internet and how would I count this? Let me express it loosely: the share of HTTP requests (by volume of requests, not by bandwidth of data and not just counting browsers). I don’t know how to measure it and we can debate the numbers in December and I guess we can all end up being right depending on what we think is the right way to count!

Who am I to tell? I’m just a person deeply interested in protocols and HTTP/2, so I’ve been involved in the HTTP work group for years and I also work on several HTTP/2 implementations. You can guess as well as I, but this just happens to be my blog!

The HTTP/2 Implementations wiki page currently lists 36 different implementations. Let’s take a closer look at the current situation and prospects in some areas.


Firefox and Chome have solid support since a while back. Just use a recent version and you’re good.

Internet Explorer has been shown in a tech preview that spoke HTTP/2 fine. So, run that or wait for it to ship in a public version soon.

There are no news about this from Apple regarding support in Safari. Give up on them and switch over to a browser that keeps up!

Other browsers? Ask them what they do, or replace them with a browser that supports HTTP/2 already.

My estimate: By the end of 2015 the leading browsers with a market share way over 50% combined will support HTTP/2.

Server software

Apache HTTPd is still the most popular web server software on the planet. mod_h2 is a recent module for it that can speak HTTP/2 – still in “alpha” state. Give it time and help out in other ways and it will pay off.

Nginx has told the world they’ll ship HTTP/2 support by the end of 2015.

IIS was showing off HTTP/2 in the Windows 10 tech preview.

H2O is a newcomer on the market with focus on performance and they ship with HTTP/2 support since a while back already.

nghttp2 offers a HTTP/2 => HTTP/1.1 proxy (and lots more) to front your old server with and can then help you deploy HTTP/2 at once.

Apache Traffic Server supports HTTP/2 fine. Will show up in a release soon.

Also, netty, jetty and others are already on board.

HTTPS initiatives like Let’s Encrypt, helps to make it even easier to deploy and run HTTPS on your own sites which will smooth the way for HTTP/2 deployments on smaller sites as well. Getting sites onto the TLS train will remain a hurdle and will be perhaps the single biggest obstacle to get even more adoption.

My estimate: By the end of 2015 the leading HTTP server products with a market share of more than 80% of the server market will support HTTP/2.


Squid works on HTTP/2 support.

HAproxy? I haven’t gotten a straight answer from that team, but Willy Tarreau has been actively participating in the HTTP/2 work all the time so I expect them to have work in progress.

While very critical to the protocol, PHK of the Varnish project has said that Varnish will support it if it gets traction.

My estimate: By the end of 2015, the leading proxy software projects will start to have or are already shipping HTTP/2 support.


Google (including Youtube and other sites in the Google family) and Twitter have ran HTTP/2 enabled for months already.

Lots of existing services offer SPDY today and I would imagine most of them are considering and pondering on how to switch to HTTP/2 as Chrome has already announced them going to drop SPDY during 2016 and Firefox will also abandon SPDY at some point.

My estimate: By the end of 2015 lots of the top sites of the world will be serving HTTP/2 or will be working on doing it.

Content Delivery Networks

Akamai plans to ship HTTP/2 by the end of the year. Cloudflare have stated that they “will support HTTP/2 once NGINX with it becomes available“.

Amazon has not given any response publicly that I can find for when they will support HTTP/2 on their services.

Not a totally bright situation but I also believe (or hope) that as soon as one or two of the bigger CDN players start to offer HTTP/2 the others might feel a bigger pressure to follow suit.

Non-browser clients

curl and libcurl support HTTP/2 since months back, and the HTTP/2 implementations page lists available implementations for just about all major languages now. Like node-http2 for javascript, http2-perl, http2 for Go, Hyper for Python, OkHttp for Java, http-2 for Ruby and more. If you do HTTP today, you should be able to switch over to HTTP/2 relatively easy.


I’m sure I’ve forgotten a few obvious points but I might update this as we go as soon as my dear readers point out my faults and mistakes!

How long is HTTP/1.1 going to be around?

My estimate: HTTP 1.1 will be around for many years to come. There is going to be a double-digit percentage share of the existing sites on the Internet (and who knows how many that aren’t even accessible from the Internet) for the foreseeable future. For technical reasons, for philosophical reasons and for good old we’ll-never-touch-it-again reasons.

The survey

Finally, I asked friends on twitter, G+ and Facebook what they think the HTTP/2 share would be by the end of 2015 with the help of a little poll. This does of course not make it into any sound or statistically safe number but is still just a collection of what a set of random people guessed. A quick poll to get a rough feel. This is how the 64 responses I received were distributed:

http2 share at end of 2015

Evidently, if you take a median out of these results you can see that the middle point is between 5-10 and 10-15. I’ll make it easy and say that the poll showed a group estimate on 10%. Ten percent of the total HTTP traffic to be HTTP/2 at the end of 2015.

I didn’t vote here but I would’ve checked the 15-20 choice, thus a fair bit over the median but only slightly into the top quarter..

In plain numbers this was the distribution of the guesses:

0-5% 29.1% (19)
5-10% 21.8% (13)
10-15% 14.5% (10)
15-20% 10.9% (7)
20-25% 9.1% (6)
25-30% 3.6% (2)
30-40% 3.6% (3)
40-50% 3.6% (2)
more than 50% 3.6% (2)

12 thoughts on “The state and rate of HTTP/2 adoption”

  1. Maybe for the share it’s better to focus on what we can actually measure.

    Traffic share in terms of HTTP requests will be very hard to evaluate. Let me create the Single Point Of Fatness :p aka sites which are more likely to use AND to publish data about HTTP requests are… already sites with high traffic. So indeed you will get high numbers. If we were asking Akamai proxies, we would have also the same story too, because Akamai clients are… big sites which need HTTP/2.0

    I think we should look at shares from different angles. So we understand what is happening more than declaring failure or success (which is not very interesting in the end).

    Some ideas to measure:

    1. How many servers are talking HTTP/2.0? (aka twitter does million of requests, it’s still just a little number of domains.)
    2. stats from 1 but distributed by countries.
    3. stats from 1 but distributed by hosting operators (probably IP ranges).
    4. How many browsers are currently asking the UPGRADE?
    5. Stats from 4 but distributed by devices type (mobile, desktop)
    6. Stats from 4 but distributed by countries.

    I think the adoption story will reveal some infrastructure hierarchies. Switching to HTTP/2.0 without changing for example old techniques of optimization can become counter effective. So the cost of upgrading is not zero for small companies. It’s not just about upgrading the server.

  2. @Daniel: SPDY is a different protocol and they have not said anything publicly about Safari supporting HTTP/2 (to my knowledge). We can only presume (or hope) that they are working on it.

  3. @karl: yeah, we can trim and discuss how to measure. I suspect it will mostly boil down to what numbers companies will make available (or not) for us to see and count.

  4. Still cannot get an answer as to if/when WebLogic will have HTTP/2 support. Contacting Oracle doesn’t seem to help either.

  5. is the JSR for Servlet 4.0 (including HTTP/2 support) which proposed for inclusion in Java EE 8. So whatever version of WebLogic, JBoss, WebSphere etc that want to support EE 8 should have it.

    Some EE implementations already support it as a protocol, but there’s not yet a standardised Java API to handle all the bits that are different than HTTP/1.1

  6. @George: failing compliance tests right now isn’t such a big deal I’d say. It is still early days and we will of course fix HTTP/2 implementations everywhere going forward.

    This said: if you find compliance or other HTTP/2 problems in existing implementations, do submit bug reports where suitable! I dare to claim that most implementers are eager to get it done right.

  7. You say that by the end of the year most major web server software packages will be HTTP2-capable. I think you’re probably right, but that’s irrelevant.

    How long will it take the people who run the servers themselves to upgrade? There’s still people running Apache 1.x and PHP 5.2, despite both being beyond ancient in web terms. Web hosts are SLOW, and will usually lag distribution LTS releases and then some. Corporate networks tend to use the oldest software they can possibly find, almost on principle. (In the name of “stability”.)

    I would *love* it if I could count on HTTP2 support for my web sites/web apps within a year or two, but the long-tail of stubborn refuse-to-upgraders is very very long. If we can’t finally put a stake in the heart of IE 7/8 (it’s a struggle), how are we going to stake HTTP1?

    I’m sure the mega players will be on board quickly, but that doesn’t help me for architecting my applications to benefit from HTTP2. (Eg, not aggregating CSS because it’s not faster to preload instead.)

  8. @Larry: I’m perfectly aware of how LOTS of sites will not be fast to upgrade and a certain amount will never upgrade. I’m not denying that. I do however believe that the big ones, the medium ones and the tech savvy users will update not too far away in the future and that will be enough to achieve the usage numbers I predict.

    But I also just predict, I can very well end up completely wrong.

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