Category Archives: Web

web stuff

copy as curl

Using curl to perform an operation a user just managed to do with his or her browser is one of the more common requests and areas people ask for help about.

How do you get a curl command line to get a resource, just like the browser would get it, nice and easy? Both Chrome and Firefox have provided this feature for quite some time already!

From Firefox

You get the site shown with Firefox’s network tools.  You then right-click on the specific request you want to repeat in the “Web Developer->Network” tool when you see the HTTP traffic, and in the menu that appears you select “Copy as cURL”. Like this screenshot below shows. The operation then generates a curl command line to your clipboard and you can then paste that into your favorite shell window. This feature is available by default in all Firefox installations.


From Chrome

When you pop up the More tools->Developer mode in Chrome, and you select the Network tab you see the HTTP traffic used to get the resources of the site. On the line of the specific resource you’re interested in, you right-click with the mouse and you select “Copy as cURL” and it’ll generate a command line for you in your clipboard. Paste that in a shell to get a curl command line  that makes the transfer. This feature is available by default in all Chome and Chromium installations.


On Firefox, without using the devtools

If this is something you’d like to get done more often, you probably find using the developer tools a bit inconvenient and cumbersome to pop up just to get the command line copied. Then cliget is the perfect add-on for you as it gives you a new option in the right-click menu, so you can get a quick command line generated really quickly, like this example when I right-click an image in Firefox:


This post was not bought

coinsAt times I post blog articles that get the view counter go up to and beyond 50,000 views. This puts me in a position where I get offers from companies to mention them or to “cooperate” on further blog posts that would somehow push their agenda or businesses.

I also get the more simple offers of adding random ads or “text only information” on specific individual pages on my sites that some SEO person out there figured out could potentially attract audience that search for specific terms.

I’ve even gotten offers from a company to sell off my server logs. Allegedly to help them work on anti-fraud so possibly for a good cause, but still…

This is by no counts a “big” blog or site, yet I get a steady stream of individuals and companies offering me money to give up a piece of my soul. I can only imagine what more popular sites get and it is clear that someone with a less strict standpoint than mine could easily make an extra income that way.

I turn down all those examples of “easy money”.

I want to be able to look you, my dear readers, straight in the eyes when I say that what’s written here are my own words and the opinions revealed are my own – even if of course you may not agree with me and I may do mistakes and be completely wrong at times or even many times. You can rest assured that I did the mistakes on my own and I was not paid by anyone to do them.

I’ve also removed ads from most of my sites and I don’t run external analytic scripts, minimizing the privacy intrusions and optimizing the contents: the stuff downloaded from my sites are what your browser needs to render the page. Not heaps of useless crap to show ads or to help anyone track you (in order to show more targeted ads).

I don’t judge others’ actions based on how I decide to run my blog. I’m in a fortunate position to take this stand, I realize that.

Still biased of course

This all said, I’m still employed by a company (Mozilla) that pays my salary and I work on several projects that are dear to me so of course I will show bias to some subjects. I don’t claim to have an objective view on things and I don’t even try to have that. When I write posts here, they come colored by my background and by what I am.

TCP tuning for HTTP

I’m the author of a brand new internet-draft that I submitted just the other day. The title is TCP Tuning for HTTP,  and the intent is to gather a set of current best practices for HTTP implementers; to share and distribute knowledge we’ve gathered over the years. Clients, servers and intermediaries. For HTTP/1.1 as well as HTTP/2.

I’m now awaiting, expecting and looking forward to feedback, criticisms and additional content for this document so that it can become the resource I’d like it to be.

How to contribute to this?

  1.  ideally, send your feedback to the HTTPbis mailing list,
  2. or submit an issue or pull-request on github for the
  3. or simply email me your comments: daniel <at>

I’ve been participating first passively and more and more actively over the years within the IETF, mostly in the HTTPbis working group. I think open protocols and open standards are important and I like being part of making them reality. I have the utmost respect and admiration for those who are involved in putting the RFCs together and thus improve the world we live in, step by step.

For a long while I’ve been wanting  to step up and “pull my weight” too,  to become a better participant in this area, and I’m happy to now finally take this step. Hopefully this is just the first step of many more to come.

(Psssst: While gathering feedback and updating the git version, the current work in progress version of the draft is always visible here.)

h2 performance at Velocity NYC

Tuesday October 13th 2015 I co-presented a talk at the Velocity conference in NYC together with Ragnar Lönn of Loadimpact. Ragnar is a friend of mine and another Swede.

Daniel and Ragnar at VelocityThe presentation was split up in two parts, in which I laid out the foundations of HTTP/2 in the first part, and Ragnar then presented the results of his performance study in the second part.

I think an interesting take away from the study is the following.

Existing sites are usually having a lot of resources that need to get downloaded. An average site has around one hundred now and the number is increasing. Those resources often have dependencies or trigger subsequent transfers. Like a HTML file gets parsed and then a CSS file is downloaded and once the CSS is downloaded it gets parsed and images specified in there are downloaded. It easily gets even more “steps” like that when downloading javascript, that triggers more javascript that renders parts of the page that causes more resources to get downloaded.

velocity room

Nothing new there, right? But when switching a site like that over to HTTP/2 the performance gain will be capped at a certain percentage no matter how large latency you have to the site because what limits such a site to perform well is the time it takes to get to the end of the slowest “dependency chain”. It is less of an issue with HTTP/1.1 since if the resources are from the same site, browsers won’t do more than 6 requests in parallel anyway (on the 6 separate TCP connections it’ll use).

It becomes evident that in order to make such a site really benefit from HTTP/2, the site would have to be modified ever so slightly so that it would deliver its contents with shorter chains and allow the browsers to get more of the resources earlier, in parallel rather than serially.

The actual talk

Splitting up a presentation in two parts with two talkers is more difficult than doing it yourself. I think we did a decent job and we ended the presentation early. It enabled us to answer to a lot of questions and we were actually quite bombarded with them – all relevant and well considered and I think we managed to bring more to the room thanks to them. A lot of the questions were about more generic HTTP/2 and deployments though and not all exactly about the performance study of the presentation.

The audience gave us an average score of 3.74 out of 5. Not too shabby. The room seated 360 persons but it wasn’t completely filled up.

Talked HTTP/2 at ApacheCon

I was invited as one of the speakers at the ApacheCon core conference in Budapest, Hungary on October 1-2, 2015.


I was once again spreading the news about HTTP/2, why it was made and how it works and of course: updated numbers on adoption right now.

The talk was unfortunately not filmed, but I’ve put my slides for this version of my talk online. Readers of this blog and those who’ve seen my presentations before will recognize large parts of it.

Following my talk was talks about mod_http2, the Apache module for HTTP/2 that will be coming in the upcoming 2.4.17 release of Apache Httpd, explained by its author Stefan Eissing. The name of the module was actually a bit of a surprise to me since it has been known as just mod_h2 for its entire life time up until now.

William A Rowe took us through the state of TLS for the main Apache servers and yeah, the state seem to be pretty good and they’re coming along really well. TLS and then HTTPS is important as that’s really a prerequisite for HTTP/2

I also got to listen to Mark Thomas explain the agonies of making Tomcat support HTTP/2, and then perhaps especially how ALPN and a good set of ciphers are hard to get in Java.

Jean-Frederic Clere then explained how to activate HTTP/2 on all the Apache servers (tomcat, httpd and traffic server) and a little about their HTTP/2 state, following with an explanation how they worked on tomcat to make that use OpenSSL for the TLS layer (including ALPN) to avoid the deadlock of decent TLS support in Java.

All in all, a great track and splendid talks with deep technical content. Exactly the way I like it. Thanks everyone. Apachecon certainly delivered for me! Twas fun.

libbrotli is brotli in lib form

Brotli is this new cool compression algorithm that Firefox now has support for in Content-Encoding, Chrome will too soon and Eric Lawrence wrote up this nice summary about.

So I’d love to see brotli supported as a Content-Encoding in curl too, and then we just basically have to write some conditional code to detect the brotli library, add the adaption code for it and we should be in a good position. But…

There is (was) no brotli library!

It turns out the brotli team just writes their code to be linked with their tools, without making any library nor making it easy to install and use for third party applications.

an unmotivated circle sawWe can’t have it like that! I rolled up my imaginary sleeves (imaginary since my swag tshirt doesn’t really have sleeves) and I now offer libbrotli to the world. It is just a bunch of files and a build system that sucks in the brotli upstream repo as a submodule and then it builds a decoder library (brotlidec) and an encoder library (brotlienc) out of them. So there’s no code of our own here. Just building on top of the great stuff done by others.

It’s not complicated. It’s nothing fancy. But you can configure, make and make install two libraries and I can now go on and write a curl adaption for this library so that we can get brotli support for it done. Ideally, this (making a library) is something the brotli project will do on their own at some point, but until they do I don’t mind handling this.

As always, dive in and try it out, file any issues you find and send us your pull-requests for everything you can help us out with!

Yours truly on “kodsnack”

kodsnackKodsnack is a Swedish-speaking weekly podcast with a small team of web/app- developers discussing their experiences and thoughts on and around software development.

I was invited to participate a week ago or so, and I had a great time. Not surprisingly, the topics at hand moved a lot around curl, Firefox and HTTP/2. The recorded episode has now gone live, today.

You can find kodsnack episode 120 here, and again, it is all Swedish.

HTTP/2 – 115 days with the RFC

http2Back in March 2015, I asked friends for a forecast on how much HTTP traffic that will be HTTP/2 by the end of the year and we arrived at about 10% as a group. Are we getting there? Remember that RFC 7540 was published on May 15th, so it is still less than 4 months old!

The HTTP/2 implementations page now lists almost 40 reasonably up-to-date implementations.


Since then, all browsers used by the vast majority of people have stated that they have or will have HTTP/2 support soon (Firefox, Chrome, Edge, Safari and Opera – including Firefox and Chrome on Android and Safari on iPhone). Even OS support is coming: on iOS 9 the support is coming as we speak and the windows HTTP library is getting HTTP/2 support. The adoption rate so far is not limited by the clients.

Unfortunately, the WGet summer of code project to add HTTP/2 support failed.

(I have high hopes for getting a HTTP/2 enabled curl into Debian soon as they’ve just packaged a new enough nghttp2 library. If things go well, this leads the way for other distros too.)


Server-side we see Apache’s mod_h2 module ship in a public release soon (possibly in a httpd version 2.4 series release), nginx has this alpha patch I’ve already mentioned and Apache Traffic Server (ATS) has already shipped h2 support for a while and my friends tell me that 6.0 has fixed numerous of their initial bugs. IIS 10 for Windows 10 was released on July 29th 2015 and supports HTTP/2. H2O and nghttp2 have shipped HTTP/2 for a long time by now. I would say that the infrastructure offering is starting to look really good! Around the end of the year it’ll look even better than today.

Of course we’re still seeing HTTP/2 only deployed over HTTPS so HTTP/2 cannot currently get more popular than HTTPS is but there’s also no real reason for a site using HTTPS today to not provide HTTP/2 within the near future. I think there’s a real possibility that we go above 10% use already in 2015 and at least for browser traffic to HTTPS sites we should be able to that almost every single HTTPS site will go HTTP/2 during 2016.

The delayed start of letsencrypt has also delayed more and easier HTTPS adoption.

Still catching up

I’m waiting to see the intermediaries really catch up. Varnish, Squid and HAProxy I believe all are planning to support it to at least some extent, but I’ve not yet seen them release a version with HTTP/2 enabled.

I hear there’s still not a good HTTP/2 story on Android and its stock HTTP library, although you can in fact run libcurl HTTP/2 enabled even there, and I believe there are other stand-alone libs for Android that support HTTP/2 too, like OkHttp for example.

Firefox numbers

Firefox Nightly screenshotThe latest stable Firefox release right now is version 40. It counts 13% HTTP/2 responses among all HTTP responses. Counted as a share of the transactions going over HTTPS, the share is roughly 27%! (Since Firefox 40 counts 47% of the transactions as HTTPS.)

This is certainly showing a share of the high volume sites of course, but there are also several very high volume sites that have not yet gone HTTP/2, like Facebook, Yahoo, Amazon, Wikipedia and more…

The IPv6 comparison

Right, it is not a fair comparison, but… The first IPv6 RFC has been out for almost twenty years and the adoption is right now at about 8.4% globally.

Content over HTTP/2

cdn77 logoRoughly a week ago, on August 19, announced that they are the “first CDN to publicly offer HTTP/2 support for all customers, without ‘beta’ limitations”. They followed up just hours later with a demo site showing off how HTTP/2 might perform side by side with a HTTP/1.1 example. And yes, the big competitor CDNs are not yet offering HTTP/2 support it seems.

Their demo site initially got critized for not being realistic and for showing HTTP/2 to be way better in comparison that what a real life scenario would be more likely to look like, and it was also subsequently updated fairly quickly. It is useful to compare with the similarly designed previously existing demo sites hosted by Akamai and the Go project.

NGINX logocdn77’s offering is built on nginx’s alpha patch for HTTP/2 that was anounced just two weeks ago. I believe nginx’s full release is still planned to happen by the end of this year.

I’ve talked with cdn77’s Jakub Straka and their lead developer Honza about their HTTP/2 efforts, and since I suspect there are a few others in my audience who’re also similarly curious I’m offering this interview-style posting here, intertwined with my own comments and thoughts. It is not just a big ad for this company, but since they’re early players on this field I figure their view and comments on this are worth reading!

I’ve been in touch with more than one person who’ve expressed their surprise and awe over the fact that they’re using this early patch for nginx to run in production. So I had to ask them about that. Below, their comments are all prefixed with CDN77 and shown using italics.


CDN77: “Yes, we are running the alpha patch, which is basically a slightly modified SPDY. In the past we have been in touch with the Nginx team and exchanged tips and ideas, the same way we plan to work on the alpha patch in the future.

We’re actually pretty careful when deploying new and potentially unstable packages into production. We have separate servers for http2 and we are monitoring them 24/7 for any exceptions. We also have dedicated developers who debug any issues we are facing with these machines. We would never jeopardize the stability of our current network.

I’m not an expert on neither server-side HTTP/2 nor nginx in particular , but I think I read somewhere that the nginx HTTP/2 patch removes the SPDY support in favor of the new protocol.

CDN77: “You are right. HTTP/2 patch rewrites SPDY into the HTTP/2, so the SPDY is no longer supported after applying the patch. Since we have HTTP/2 running on separate servers, we still have SPDY support on the rest of the network.”

Did the team at cdn77 at all consider using something else than nginx for HTTP/2, like the promising newcomer h2o?

CDN77: “Not at all. Nginx is a clear choice for us. Its architecture and modularity is awesome. It is also very reliable and it has a pretty long history.

On scale

Can you share some of the biggest hurdles you had to overcome to deploy HTTP/2 on this scale with nginx?

CDN77: “Since nobody has tried the patch in such a scale ever before, we had to make sure it will hold even under pressure and needed to create a load heavy testing environment. We used servers from our partner company and their 10G uplinks to create intensive ghost traffic. Also, it was important to make sure that supporting tools and applications are HTTP/2 ready – not all of them were. We needed to adjust the way we monitor and control servers in few cases.

There are a few bugs in Nginx that appear mainly in association with the longer-lived connections. They cause issues with the application layer and consume more resources. To be able to accommodate HTTP/2 and still keep necessary network redundancies, we needed to upgrade our network significantly.

I read this as an indication that the nginx patch isn’t perfected just yet rather than signifying that http2 is special. Perhaps also that http2 connections might use a larger footprint in nginx than good old http1 connections do.

Jakub mentioned they see average “performance savings” in the order of 20 to 60 percent depending on sites and contents with the switch to h2, but their traffic amounts haven’t been that large yet:

CDN77: “So far, only a fraction of the traffic is running via HTTP/2, but that is understandable since we launched the support few days ago. On the first day, only about 0.45% of the traffic was HTTP/2 and a big part of this was our own demo site. Over the weekend, we saw impressive adoption rate and the total HTTP/2 traffic accounts for more than 0.8% now, all that with the portion of our own traffic in this dropping dramatically. We expect to be pushing around 1.2% – 1.5% of total traffic over HTTP/2 till the end of this week.

Understandably, it is ramping up. Still, Firefox telemetry is showing at least 10% of the total traffic over HTTP/2 already.

Future of HTTPS and HTTP/2?

Whttp2 logohile I’m talking to a CDN operator, I figured I should poll their view on HTTPS going forward! Will the fact that all browsers only support h2 over HTTPS push more of your customers and your traffic in general over to HTTP, you think?

CDN77: “This is not easy to predict. There is encryption overhead, but HTTP/2 comes with header compression and it is binary. So at this single point, the advantages and disadvantages zero out. Also, the use of HTTPS is rising rapidly even on the older protocol, so we don’t consider this an issue at all.

In general, from a CDN perspective and as someone who just deployed this on a fairly large scale, what’s your general perception of what http2 means going forward?

CDN77: “We believe that this is a huge step forward in how we distribute content online and as a CDN company, we are especially excited as it concerns the very core of our business. From the new features, we have great expectations about cache invalidation that is being discussed right now.

Thanks to Jakub, Honza and Tomáš of cdn77 for providing answers and info. We live in exciting times.