curl, or libcurl specifically, is probably the world’s most popular and widely used HTTP client side library counting more than six billion installs.
curl is a rock solid and feature-packed library that supports a huge amount of protocols and capabilities that surpass most competitors. But this comes at a cost: it is not the smallest library you can find.
Within a 100K
Instead of being happy with getting told that curl is “too big” for certain use cases, I set a goal for myself: make it possible to builda version of curl that can do HTTPS and fit in 100K (including the wolfSSL TLS library) on a typical 32 bit architecture.
As a comparison, the tiny-curl shared library when built on an x86-64 Linux, is smaller than 25% of the size as the default Debian shipped library is.
But let’s not stop there. Users with this kind of strict size requirements are rarely running a full Linux installation or similar OS. If you are sensitive about storage to the exact kilobyte level, you usually run a more slimmed down OS as well – so I decided that my initial tiny-curl effort should be done on FreeRTOS. That’s a fairly popular and free RTOS for the more resource constrained devices.
This port is still rough and I expect us to release follow-up releases soon that improves the FreeRTOS port and ideally also adds support for other popular RTOSes. Which RTOS would you like to support for that isn’t already supported?
Offer the libcurl API for HTTPS on FreeRTOS, within 100 kilobytes.
I strongly believe that the power of having libcurl in your embedded devices is partly powered by the libcurl API. The API that you can use for libcurl on any platform, that’s been around for a very long time and for which you can find numerous examples for on the Internet and in libcurl’s extensive documentation. Maintaining support for the API was of the highest priority.
My secondary goal was to patch as clean as possible so that we can upstream patches into the main curl source tree for the changes makes sense and that aren’t disturbing to the general code base, and for the work that we can’t we should be able to rebase on top of the curl code base with as little obstruction as possible going forward.
Keep the HTTPS basics
I just want to do HTTPS GET
That’s the mantra here. My patch disables a lot of protocols and features:
No protocols except HTTP(S) are supported
No cookie support
No date parsing
No HTTP authentication
No .netrc parsing
No HTTP multi-part formposts
No shuffled DNS support
No built-in progress meter
Although they’re all disabled individually so it is still easy to enable one or more of these for specific builds.
Most of the patches in tiny-curl are being upstreamed into curl in the #3844 pull request. I intend to upstream most, if not all, of the tiny-curl work over time.
The FreeRTOS port of tiny-curl is licensed GPLv3 and not MIT like the rest of curl. This is an experiment to see how we can do curl work like this in a sustainable way. If you want this under another license, we’re open for business over at wolfSSL!
I view myself as primarily a software developer. Perhaps secondary as someone who’s somewhat knowledgeable in networking and is participating in protocol development and discussions. I do not regularly proclaim myself to be a “speaker” or someone who’s even very good at talking in front of people.
Time to wake up and face reality? I’m slowly starting to realize that I’m actually doing more presentations than ever before in my life and I’m enjoying it.
Since October 2015 I’ve done 53 talks and presentations in front of audiences – in ten countries. That’s one presentation done every 25 days on average. (The start date of this count is a little random but it just happens that I started to keep a proper log then.) I’ve talked to huge audiences and to small. I done presentations that were appreciated and I’ve done some that were less successful.
My increased frequency in speaking engagements coincides with me starting to work full-time from home back in 2014. Going to places to speak is one way to get out of the house and see the “real world” a little bit and see what the real people are doing. And a chance to hang out with humans for a change. Besides, I only ever talk on topics that are dear to me and that I know intimately well so I rarely feel pressure when delivering them. 2014 – 2015 was also the time frame when HTTP/2 was being finalized and the general curiosity on that new protocol version helped me find opportunities back then.
Public speaking is like most other things: surprisingly enough, practice actually makes you better at it! I still have a lot to learn and improve, but speaking many times has for example made me better at figuring out roughly how long time I need to deliver a particular talk. It has taught me to “find myself” better when presenting and be more relaxed and the real me – no need to put up a facade of some kind or pretend. People like seeing that there’s a real person there.
I’m not even getting that terribly nervous before my talks anymore. I used to really get a raised pulse for the first 45 talks or so, but by doing it over and over and over I think the practice has made me more secure and more relaxed in my attitude to the audience and the topics. I think it has made me a slightly better presenter and it certainly makes me enjoy it more.
I’m not “a good presenter”. I can deliver a talk and I can do it with dignity and I think the audience is satisfied with me in most cases, but by watching actual good presenters talk I realize that I still have a long journey ahead of me. Of course, parts of the explanation is that, to connect with the beginning of this post, I’m a developer. I don’t talk for a living and I actually very rarely practice my presentations very much because I don’t feel I can spend that time.
Some of the things that are still difficult include:
The money issue. I actually am a developer and that’s what I do for a living. Taking time off the development to prepare a presentation, travel to a distant place, sacrifice my spare time for one or more days and communicating something interesting to an audience that demands and expects it to be both good and reasonably entertaining takes time away from that development. Getting travel and accommodation compensated is awesome but unfortunately not enough. I need to insist on getting paid for this. I frequently turn down speaking opportunities when they can’t pay me for my time.
Saying no. Oh my god do I have a hard time to do this. This year, I’ve been invited to so many different conferences and the invitations keep flying in. For every single received invitation, I get this warm and comfy feeling and I feel honored and humbled by the fact that someone actually wants me to come to their conference or gathering to talk. There’s the calendar problem: I can’t be in two places at once. Then I also can’t plan events too close to each other in time to avoid them holding up “real work” too much or to become too much of a nuisance to my family. Sometimes there’s also the financial dilemma: if I can’t get compensation, it gets tricky for me to do it, no matter how good the conference seems to be and the noble cause they’re working for.
Feedback. To determine what parts of the presentation that should be improved for the next time I speak of the same or similar topic, which parts should be removed and if something should be expanded, figuring what works and what doesn’t work is vital. For most talks I’ve done, there’s been no formal way to provide or receive this feedback, and for the small percentage that had a formal feedback form or a scoring system or similar, taking care of a bunch of distributed grades (for example “your talk was graded 4.2 on a scale between 1 and 5”) and random comments – either positive or negative – is really hard… I get the best feedback from close friends who dare to tell me the truth as it is.
Conforming to silly formats. Slightly different, but some places want me to send me my slides in, either a long time before the event (I’ve had people ask me to provide way over a week(!) before), or they dictate that the slides should be sent to them using Microsoft Powerpoint, PDF or some other silly format. I want to use my own preferred tools when designing presentations as I need to be able to reuse the material for more and future presentations. Sure, I can convert to other formats but that usually ruins formatting and design. Then a lot the time and sweat I put into making a fine and good-looking presentation is more or less discarded! Fortunately, most places let me plug in my laptop and everything is fine!
As a little service to potential audience members and conference organizers, I’m listing all my upcoming speaking engagements on a dedicated page on my web site:
I try to keep that page updated to reflect current reality. It also shows that some organizers are forward-planning waaaay in advance…
Invite someone like me to talk?
Here’s some advice on how to invite a speaker (like me) with style:
Ask well in advance (more than 2-3 months preferably, probably not more than 9). When I agree to a talk, others who ask for talks in close proximity to that date will get declined. I get a surprisingly large amount of invitations for events just a month into the future or so, and it rarely works for me to get those into my calendar in that time frame.
Do not assume for-free delivery. I think it is good tone of you to address the price/charge situation, if not in the first contact email at least in the following discussion. If you cannot pay, that’s also useful information to provide early.
If the time or duration of the talk you’d like is “unusual” (ie not 30-60 minutes) do spell that out early on.
Surprisingly often I get invited to talk without a specified topic or title. The inviter then expects me to present that. Since you contact me you clearly had some kind of vision of what a talk by me would entail, it would make my life easier if that vision was conveyed as it could certainly help me produce a talk subject that will work!
What I bring
To every presentation I do, I bring my laptop. It has HDMI and USB-C ports. I also carry a HDMI-to-VGA adapter for the few installations that still use the old “projector port”. Places that need something else than those ports tend to have their own converters already since they’re then used with equipment not being fitted for their requirements.
I always bring my own clicker (the “remote” with which I can advance to next slide). I never use the laser-pointer feature, but I like being able to move around on the stage and not have to stand close to the keyboard when I present.
I never create my presentations with video or sound in them, and I don’t do presentations that need Internet access. All this to simplify and to reduce the risk of problems.
I work hard on limiting the amount of text on each slide, but I also acknowledge that if a slide set should have value after-the-fact there needs to be a certain amount. I’m a fan of revealing the text or graphics step-by-step on the slides to avoid having half the audience reading ahead on the slide and not listening.
I’ve settled on 16:9 ratio for all presentations. Luckily, the remaining 4:3 projectors are now scarce.
I always make and bring a backup of my presentations in PDF format so that basically “any” computer could display that in case of emergency. Like if my laptop dies. As mentioned above, PDF is not an ideal format, but as a backup it works.
(This is a repost of the answer I posted on stackoverflow for this question. This answer immediately became my most ever upvoted answer on stackoverflow with 516 upvotes during the 48 hours it was up before a moderator deleted it for unspecified reasons. It had then already been marked “on hold” for being “primarily opinion- based” and then locked but kept: “exists because it has historical significance”. But apparently that wasn’t good enough. I’ve saved a screenshot of the deletion. Debated on meta.stackoverflow.com. Status now: it was brought back but remains locked.)
I’m Daniel Stenberg.
I made curl
I founded the curl project back in 1998, I wrote the initial curl version and I created libcurl. I’ve written more than half of all the 24,000 commits done in the source code repository up to this point in time. I’m still the lead developer of the project. To a large extent, curl is my baby.
I shipped the first version of curl as open source since I wanted to “give back” to the open source world that had given me so much code already. I had used so much open source and I wanted to be as cool as the other open source authors.
Thanks to it being open source, literally thousands of people have been able to help us out over the years and have improved the products, the documentation. the web site and just about every other detail around the project. curl and libcurl would never have become the products that they are today were they not open source. The list of contributors now surpass 1900 names and currently the list grows with a few hundred names per year.
Thanks to curl and libcurl being open source and liberally licensed, they were immediately adopted in numerous products and soon shipped by operating systems and Linux distributions everywhere thus getting a reach beyond imagination.
Thanks to them being “everywhere”, available and liberally licensed they got adopted and used everywhere and by everyone. It created a defacto transfer library standard.
At an estimated six billion installations world wide, we can safely say that curl is the most widely used internet transfer library in the world. It simply would not have gone there had it not been open source. curl runs in billions of mobile phones, a billion Windows 10 installations, in a half a billion games and several hundred million TVs – and more.
Should I have released it with proprietary license instead and charged users for it? It never occured to me, and it wouldn’t have worked because I would never had managed to create this kind of stellar project on my own. And projects and companies wouldn’t have used it.
Why do I still work on curl?
Now, why do I and my fellow curl developers still continue to develop curl and give it away for free to the world?
I can’t speak for my fellow project team members. We all participate in this for our own reasons.
I think it’s still the right thing to do. I’m proud of what we’ve accomplished and I truly want to make the world a better place and I think curl does its little part in this.
There are still bugs to fix and features to add!
curl is free but my time is not. I still have a job and someone still has to pay someone for me to get paid every month so that I can put food on the table for my family. I charge customers and companies to help them with curl. You too can get my help for a fee, which then indirectly helps making sure that curl continues to evolve, remain free and the kick-ass product it is.
curl was my spare time project for twenty years before I started working with it full time. I’ve had great jobs and worked on awesome projects. I’ve been in a position of luxury where I could continue to work on curl on my spare time and keep shipping a quality product for free. My work on curl has given me friends, boosted my career and taken me to places I would not have been at otherwise.
I would not do it differently if I could back and do it again.
Am I proud of what we’ve done?
Yes. So insanely much.
But I’m not satisfied with this and I’m not just leaning back, happy with what we’ve done. I keep working on curl every single day, to improve, to fix bugs, to add features and to make sure curl keeps being the number one file transfer solution for the world even going forward.
We do mistakes along the way. We make the wrong decisions and sometimes we implement things in crazy ways. But to win in the end and to conquer the world is about patience and endurance and constantly going back and reconsidering previous decisions and correcting previous mistakes. To continuously iterate, polish off rough edges and gradually improve over time.
Never give in. Never stop. Fix bugs. Add features. Iterate. To the end of time.
Yeah. For real.
Do I ever get tired? Is it ever done?
Sure I get tired at times. Working on something every day for over twenty years isn’t a paved downhill road. Sometimes there are obstacles. During times things are rough. Occasionally people are just as ugly and annoying as people can be.
But curl is my life’s project and I have patience. I have thick skin and I don’t give up easily. The tough times pass and most days are awesome. I get to hang out with awesome people and the reward is knowing that my code helps driving the Internet revolution everywhere is an ego boost above normal.
curl will never be “done” and so far I think work on curl is pretty much the most fun I can imagine. Yes, I still think so even after twenty years in the driver’s seat. And as long as I think it’s fun I intend to keep at it.
(I will update this blog post with more links to videos and PDFs to presentations as they get published, so come back later in case your favorite isn’t linked already.)
The third curl developers conference, curl up 2019, is how history. We gathered in the lovely Charles University in central Prague where we sat down in an excellent class room. After the HTTP symposium on the Friday, we spent the weekend to dive in deeper in protocols and curl details.
I started off the Saturday by The state of the curl project (youtube). An overview of how we’re doing right now in terms of stats, graphs and numbers from different aspects and then something about what we’ve done the last year and a quick look at what’s not do good and what we could work on going forward.
James Fuller took the next session and his Newbie guide to contributing to libcurl presentation. Things to consider and general best practices to that could make your first steps into the project more likely to be pleasant!
Long term curl hacker Dan Fandrich (also known as “Daniel two” out of the three Daniels we have among our top committers) followed up with Writing an effective curl test where the detailed what different tests we have in curl, what they’re for and a little about how to write such tests.
After that I was back behind the desk in the classroom that we used for this event and I talked The Deprecation of legacy crap (Youtube). How and why we are removing things, some things we are removing and will soon remove and finally a little explainer on our new concept and handling of “experimental” features.
Our local hero organizer James Fuller then spoiled us completely when we got around to have dinner at a monastery with beer brewing monks and excellent food. Good food, good company and curl related dinner subjects. That’s almost heaven defined!
Daylight saving time morning and you could tell. I’m sure it was not at all related to the beers from the night before…
James Fuller fired off the day by talking to us about Curlpipe (github), a DSL for building http execution pipelines.
Robin Marx then put in the next gear and entertained us another hour with a protocol deep dive titled HTTP/3 (QUIC): the details (slides). For me personally this was a exactly what I needed as Robin clearly has kept up with more details and specifics in the QUIC and HTTP/3 protocols specifications than I’ve managed and his talk help the rest of the room get at least little bit more in sync with current development.
Jakub Nesetril and Lukáš Linhart from Apiary then talked us through what they’re doing and thinking around web based APIs and how they and their customers use curl: Real World curl usage at Apiary.
Jakub Klímek explained to us in very clear terms about current and existing problems in his talk IRIs and IDNs: Problems of non-ASCII countries. Some of the problems involve curl and while most of them have their clear explanations, I think we have to lessons to learn from this: URLs are still as messy and undocumented as ever before and that we might have some issues to fix in this area in curl.
To bring my fellow up to speed on the details of the new API introduced the last year I then made a presentation called The new URL API.
I ended up doing seven presentations during this single weekend. Not all of them stellar or delivered with elegance but I hope they were still valuable to some. I did not steal someone else’s time slot as I would gladly have given up time if we had other speakers wanted to say something. Let’s aim for more non-Daniel talkers next time!
A weekend like this is such a boost for inspiration, for morale and for my ego. All the friendly faces with the encouraging and appreciating comments will keep me going for a long time after this.
Thank you to our awesome and lovely event sponsors – shown in the curl up logo below! Without you, this sort of happening would not happen.
curl up 2020
I will of course want to see another curl up next year. There are no plans yet and we don’t know where to host. I think it is valuable to move it around but I think it is even more valuable that we have a friend on the ground in that particular city to help us out. Once this year’s event has sunken in properly and a month or two has passed, the case for and organization of next year’s conference will commence. Stay tuned, and if you want to help hosting us do let me know!
If you want commercial support, ports of curl to other operating systems or just instant help to fix your curl related problems, we’re here to help. Get in touch now! This is the premiere. This has not been offered by me or anyone else before.
I’m not sure I need to say it, but I personally have authored almost 60% of all commits in the curl source code during my more than twenty years in the project. I started the project, I’ve designed its architecture etc. There is simply no one around with my curl experience and knowledge of curl internals. You can’t buy better curl expertise.
curl has become one of the world’s most widely used software components and is the transfer engine doing a large chunk of all non-browser Internet transfers in the world today. curl has reached this level of success entirely without anyone offering commercial services around it. Still, not every company and product made out there has a team of curl experts and in this demanding time and age we know there are times when you rather hire the right team to help you out.
We are the curl experts that can help you and your team. Contact us for all and any support questions at email@example.com.
What about the curl project?
I’m heading into this new chapter of my life and the curl project with the full knowledge that this blurs the lines between my job and my spare time even more than before. But fear not!
The curl project is free and open and will remain independent of any commercial enterprise helping out customers. I realize me offering companies and organizations to deal with curl problems and solving curl issues for compensation creates new challenges and questions where boundaries go, if for nothing else for me personally. I still think this is worth pursuing and I’m sure we can figure out and handle whatever minor issues this can lead to.
My friends, the community, the users and harsh critiques on twitter will all help me stay true and honest. I know this. This should end up a plus for the curl project in general as well as for me personally. More focus, more work and more money involved in curl related activities should improve the project.
It is with great joy and excitement I take on this new step.