25 Years of curl: From a Small URL Tool to Billions of Installations

Read the introduction: Open‑source software author Daniel Stenberg proudly celebrated curl’s 25th anniversary and the release of curl 8.0.0, marking the 215th release of the command‑line tool, with a remote gathering of all contributors.

Daniel Stenberg is the well‑known author of the open‑source networking tool curl.

curl originally appeared as “cURL” to emphasize its function as a “URL client” or “client URL request library”.

curl is both a command‑line tool and a library for transferring data via URLs. When installed on a machine with command‑line access, curl can send data to servers using many network protocols and also retrieve data from them.

Any developer who has written network‑interaction programs has likely used curl.

curl is now embedded in dozens of programming languages and powers billions of devices—including cars, phones, set‑top boxes, routers, and similar products—for internal data transfer.

Daniel Stenberg says the curl project started very modestly, merely a renamed small URL transfer tool that was almost unknown in its early years.

The first version of curl was released on March 20 1998, consisting of 2,200 lines of code derived from the httpget and urlget projects.

Stenberg recalls that curl 4.0 supported only three protocols (HTTP, GOPHER, FTP) and offered 24 command‑line options.

Today, version 8.0.0 handles 28 protocols and provides 249 command‑line options.

“The first version of curl was not a special event. I had already released httpget and urlget for over a year; the new name was essentially another version,” Stenberg explains.

Shortly after its debut, curl began supporting HTTPS and TELNET.

According to Stenberg, curl was initially released under the GPL, switched to the MPL by the end of 1998, added a MIT‑like license in 2001, and dropped the MPL in 2002.

The project has become mainstream. Stenberg’s goal has simply been continuous improvement, and with contributors’ effort curl grew to hundreds of millions of installations by 2010.

Conservatively, curl is now installed on more than 10 billion devices.

As of early 2023, curl contains about 155,100 lines of code, contributions from over 2,800 people, more than 1,100 commit authors, and over 30,000 commits.

The total bounty paid for curl bug fixes exceeds US $48,000.

During the 25‑year celebration, Stenberg received many thank‑you messages, though two years earlier he also received a death threat from an unhappy user.

Stenberg lives and works in Sweden; in his anniversary post he thanked users for global support that lets him focus on development.

Initially a hobby, curl became Stenberg’s full‑time focus after he was hired by WolfSSL in 2019, and he continues to appreciate the many contributors who keep the project alive.

Although 25 years have passed, Stenberg avoids making predictions for the future, stating he simply hopes the project stays active, remains fun and useful, and that people continue to use his work.

curl may never reach a final version; just seven hours after releasing curl 8.0.0, Stenberg issued curl 8.0.1 to fix minor bugs.

Art never ends, and iterative optimization is always the present.

Author: Luo Yi

Related reading:

Microsoft donates $10,000 to the cURL open‑source project

cURL author Daniel Stenberg plans to add native JSON support to cURL

cURL founder questions Apple: “Earn billions from open source while treating developers as free tools”