How curl Became Like This

Towards the end of 1996, Daniel Stenberg was spending time writing an IRC bot for an Amiga related channel on EFnet. He then came up with the idea to make currency-exchange calculations available to Internet Relay Chat (IRC) users. All the necessary data were published on the Web; he just needed to automate their retrieval.

Daniel simply adopted an existing command-line open-source tool, httpget, that Brazilian Rafael Sagula had written and recently released version 0.1 of. After a few minor adjustments, it did just what he needed.


HttpGet 1.0 was released on April 8th 1997 with brand new HTTP proxy support.

We soon found and fixed support for getting currencies over GOPHER. Once FTP download support was added, the name of the project was changed and urlget 2.0 was released in August 1997. The http-only days were already passed.


The project slowly grew bigger. When upload capabilities were added and the name once again was misleading, a second name change was made and on March 20, 1998 curl 4 was released. (The version numbering from the previous names was kept.)

(Unrelated to this project a company called Curl Corporation registered a US trademark on the name “CURL” on May 18 1998. That company had then already registered the domain back in November of the previous year. All this was revealed to us much later.)

SSL support was added, powered by the SSLeay library.

August: first announcement of curl on

October: with the curl 4.9 release and the introduction of cookie support, curl was no longer released under the GPL license. Now we're at 4000 lines of code, we switched over to the MPL license to restrict the effects of “copyleft”.

November: configure script and reported successful compiles on several major operating systems. The never-quite-understood -F option was added and curl could now simulate quite a lot of a browser. TELNET support was added.

Curl 5 was released in December 1998 and introduced the first ever curl man page. People started making Linux RPM packages out of it.


January: DICT support added.

OpenSSL took over and SSLeay was abandoned.

May: first Debian package.

August: LDAP:// and FILE:// support added. The curl web site gets 1300 visits weekly. Moved site to

September: Released curl 6.0. 15000 lines of code.

December 28: added the project on Sourceforge and started using its services for managing the project.


Spring: major internal overhaul to provide a suitable library interface. The first non-beta release was named 7.1 and arrived in August. This offered the easy interface and turned out to be the beginning of actually getting other software and programs to be based on and powered by libcurl. Almost 20000 lines of code.

June: the curl site moves to “”

August, the curl web site gets 4000 visits weekly.

The PHP guys adopted libcurl already the same month, when the first ever third party libcurl binding showed up. CURL has been a supported module in PHP since the release of PHP 4.0.2. This would soon get followers. More than 16 different bindings exist at the time of this writing.

September: kerberos4 support was added.

November: started the work on a test suite for curl. It was later re-written from scratch again. The libcurl major SONAME number was set to 1.


January: Daniel released curl 7.5.2 under a new license again: MIT (or MPL). The MIT license is extremely liberal and can be combined with GPL in other projects. This would finally put an end to the “complaints” from people involved in GPLed projects that previously were prohibited from using libcurl while it was released under MPL only. (Due to the fact that MPL is deemed “GPL incompatible”.)

March 22: curl supports HTTP 1.1 starting with the release of 7.7. This also introduced libcurl's ability to do persistent connections. 24000 lines of code. The libcurl major SONAME number was bumped to 2 due to this overhaul. The first experimental ftps:// support was added.

August: curl is bundled in Mac OS X, 10.1. It was already becoming more and more of a standard utility of Linux distributions and a regular in the BSD ports collections. The curl web site gets 8000 visits weekly. Curl Corporation contacted Daniel to discuss “the name issue”. After Daniel's reply, they have never since got back in touch again.

September: libcurl 7.9 introduces cookie jar and curl_formadd(). During the forthcoming 7.9.x releases, we introduced the multi interface slowly and without many whistles.


June: the curl web site gets 13000 visits weekly. curl and libcurl is 35000 lines of code. Reported successful compiles on more than 40 combinations of CPUs and operating systems.

To estimate number of users of the curl tool or libcurl library is next to impossible. Around 5000 downloaded packages each week from the main site gives a hint, but the packages are mirrored extensively, bundled with numerous OS distributions and otherwise retrieved as part of other software.

September: with the release of curl 7.10 it is released under the MIT license only.


January: Started working on the distributed curl tests. The autobuilds.

February: the curl site averages at 20000 visits weekly. At any given moment, there's an average of 3 people browsing the site.

Multiple new authentication schemes are supported: Digest (May), NTLM (June) and Negotiate (June).

November: curl 7.10.8 is released. 45000 lines of code. ~55000 unique visitors to the site. Five official web mirrors.

December: full-fledged SSL for FTP is supported.


January: curl 7.11.0 introduced large file support.

June: curl 7.12.0 introduced IDN support. 10 official web mirrors.

This release bumped the major SONAME to 3 due to the removal of the curl_formparse() function

August: Curl and libcurl 7.12.1

Public curl release number:                82
Releases counted from the very beginning: 109
Available command line options:            96
Available curl_easy_setopt() options:     120
Number of public functions in libcurl:     36
Amount of public web site mirrors:         12
Number of known libcurl bindings:          26


April: GnuTLS can now optionally be used for the secure layer when curl is built.

April: Added the multi_socket() API

September: TFTP support was added.

More than 100,000 unique visitors of the curl web site. 25 mirrors.

December: security vulnerability: libcurl URL Buffer Overflow


January: We dropped support for Gopher. We found bugs in the implementation that turned out to have been introduced years ago, so with the conclusion that nobody had found out in all this time we removed it instead of fixing it.

March: security vulnerability: libcurl TFTP Packet Buffer Overflow

September: The major SONAME number for libcurl was bumped to 4 due to the removal of ftp third party transfer support.

November: Added SCP and SFTP support


February: Added support for the Mozilla NSS library to do the SSL/TLS stuff

July: security vulnerability: libcurl GnuTLS insufficient cert verification



Command line options:         128
curl_easy_setopt() options:   158
Public functions in libcurl:   58
Known libcurl bindings:        37
Contributors:                 683

145,000 unique visitors. >100 GB downloaded.


March: security vulnerability: libcurl Arbitrary File Access

April: added CMake support

August: security vulnerability: libcurl embedded zero in cert name

December: Added support for IMAP, POP3 and SMTP


January: Added support for RTSP

February: security vulnerability: libcurl data callback excessive length

March: The project switched over to use git (hosted by github) instead of CVS for source code control

May: Added support for RTMP

Added support for PolarSSL to do the SSL/TLS stuff


Public curl releases:         117
Command line options:         138
curl_easy_setopt() options:   180
Public functions in libcurl:   58
Known libcurl bindings:        39
Contributors:                 808

Gopher support added (re-added actually, see January 2006)


February: added support for the axTLS backend

April: added the cyassl backend (later renamed to WolfSSL)


July: Added support for Schannel (native Windows TLS backend) and Darwin SSL (Native Mac OS X and iOS TLS backend).

Supports metalink

October: SSH-agent support.


February: Cleaned up internals to always uses the “multi” non-blocking approach internally and only expose the blocking API with a wrapper.

September: First small steps on supporting HTTP/2 with nghttp2.

October: Removed krb4 support.

December: Happy eyeballs.


March: first real release supporting HTTP/2

September: Web site had 245,000 unique visitors and served 236GB data

SMB and SMBS support


June: support for multiplexing with HTTP/2

August: support for HTTP/2 server push

December: Public Suffix List


January: the curl tool defaults to HTTP/2 for HTTPS URLs

December: curl 7.52.0 introduced support for HTTPS-proxy!

First TLS 1.3 support


July: OSS-Fuzz started fuzzing libcurl

September: Added Multi-SSL support

The web site serves 3100 GB/month

Public curl releases:         169
Command line options:         211
curl_easy_setopt() options:   249
Public functions in libcurl:  74
Contributors:                 1609

October: SSLKEYLOGFILE support, new MIME API

November: brotli


January: new SSH backend powered by libssh

March: starting with the 1803 release of Windows 10, curl is shipped bundled with Microsoft's operating system.

July: curl shows headers using bold type face

October: added DNS-over-HTTPS (DoH) and the URL API

MesaLink is a new supported TLS backend

libcurl now does HTTP/2 (and multiplexing) by default on HTTPS URLs

curl and libcurl are installed in an estimated 5 billion instances world-wide.

October 31: Curl and libcurl 7.62.0

Public curl releases:         177
Command line options:         219
curl_easy_setopt() options:   261
Public functions in libcurl:  80
Contributors:                 1808


August: the first HTTP/3 requests with curl.

September: 7.66.0 is released and the tool offers parallel downloads