The Man Who Built The Internet's Most Essential Tool (And You've Never Heard Of Him)

There are a few pieces of software that are so fundamental to the internet that without them, the digital world as we know it would grind to a halt. You might think of the Linux kernel, or the Apache web server. But there is another, more humble tool that is just as ubiquitous, running on an estimated ten billion devices worldwide. It’s in your phone, your car, your TV, and probably even your refrigerator. It’s called curl, and for the last 25 years, it has been the quiet, tireless workhorse of the internet.

Even more remarkable than the software itself is the man behind it. curl is not the product of a massive corporation or a well-funded foundation. It is, for the most part, the life’s work of a single, dedicated programmer from Sweden named Daniel Stenberg. This is the story of how a spare-time project, started to solve a simple problem for an IRC bot, became one of the most critical pieces of infrastructure in the world.

The Accidental Beginning

In 1996, Daniel Stenberg was running an IRC bot and wanted it to provide currency exchange rates. To do this, he needed a way to automatically download the rates from a web page. He found a small command-line tool called httpget, but it had some bugs. So, he fixed them. Then he took over maintenance of the project. He added support for Gopher, then FTP. The tool’s name changed from httpget to urlget, and finally, in 1998, to curl (a play on “see URL”).

What started as a simple tool for a hobby project, had, almost by accident, become a powerful and flexible data transfer engine.

The Swiss Army Knife of Data Transfer

The power of curl lies in its simplicity and its incredible versatility. It is a command-line tool for transferring data with URLs. That’s it. But that simple description hides a staggering amount of complexity. curl supports over 25 protocols, from HTTP and FTP to SMTP and IMAP. It can handle cookies, proxies, SSL/TLS connections, and just about any other nuance of internet communication you can think of.

This is why it has become the go-to tool for developers. Need to test an API from the command line? Use curl. Need to download a file in a script? Use curl. Need to automate a complex series of web requests? Use curl.

But the command-line tool is only half the story. The real power of curl is in libcurl, the library that powers the command-line tool. libcurl allows any application to use curl’s data transfer capabilities. This is why curl is in everything. When an app on your phone needs to to download an update, it’s probably using libcurl. When your favorite game needs to fetch data from a server, it’s probably using libcurl. When your car’s infotainment system needs to connect to the internet, there’s a good chance it’s using libcurl.

The Man Behind the Curtain

For over two decades, Daniel Stenberg maintained curl as a spare-time project. He had a day job as an embedded systems consultant, and he would work on curl in the evenings, after his family had gone to bed. It was a labor of love, a commitment to building a high-quality, reliable tool for the world.

In 2019, after 21 years, he was finally able to work on curl full-time, thanks to a job at wolfSSL, a company that provides commercial support for the tool. But the project remains, as it always has been, free and open source.

Conclusion: The Power of One

The story of curl is a powerful reminder that a single, dedicated individual can have a massive impact on the world. It’s a story about the power of open source to create essential infrastructure that benefits everyone. And it’s a story about the quiet, unsung heroes of the internet, the people who build and maintain the tools that make our digital lives possible.

The next time you use an app, play a game, or watch a movie, take a moment to think about the incredible amount of work that goes on behind the scenes. And remember that somewhere, a man named Daniel Stenberg is probably fixing a bug or adding a new feature to the tool that makes it all work.

The next time you use an app, play a game, or watch a movie, take a moment to think about the incredible amount of work that goes on behind the scenes. And remember that somewhere, a man named Daniel Stenberg is probably fixing a bug or adding a new feature to the tool that makes it all work.

You can read more about the history of curl on Daniel’s blog: https://daniel.haxx.se/ You can also support the project by donating: https://curl.se/donation.html