Everything curl is an extensive guide for all things curl. The project, the command-line tool, the library, how everything started and how it came to be the useful tool it is today. It explains how we work on developing it further, what it takes to use it, how you can contribute with code or bug reports and why millions of existing users use it.

This book is meant to be interesting and useful to both casual readers and somewhat more experienced developers. It offers something for everyone to pick and choose from.

Do not read this book from front to back. Read the chapters or content you are curious about and flip back and forth as you see fit.

This book is an open source project in itself: open, completely free to download and read. Free for anyone to comment on, and available for everyone to contribute to and help out with. Send your bug reports, ideas, pull requests or critiques to us and I or someone else will work on improving the book accordingly.

This book will never be finished. I intend to keep working on it. While I may at some point consider it fairly complete, covering most aspects of the project (even if only that seems like an insurmountable goal), the curl project will continue to move so there will always be things to update in the book as well.

This book project started at the end of September 2015.

Site is the home of this book. It features the book online in a web version.

This book is also provided as a PDF and an ePUB.

The book website is hosted by Fastly. The book contents is rendered by mdBook since March 18th, 2024.


All book content is hosted on GitHub in the repository.


With the hope of becoming just a co-author of this material, I am Daniel Stenberg. I founded the curl project and I am a developer at heart—for fun and profit. I live and work in Stockholm, Sweden.

All there is to know about Daniel can be found on


If you find mistakes, omissions, errors or blatant lies in this document, please send us a refreshed version of the affected paragraph and we will amend and update. We give credit to and recognize everyone who helps out.

Preferably, you could submit errors or pull requests on the book's GitHub page.


Lots of people have reported bugs, improved sections or otherwise helped make this book the success it is. These friends include the following:

AaronChen0 on github, alawvt on github, Amin Khoshnood, amnkh on github, Anders Roxell, Angad Gill, Aris (Karim) Merchant, auktis on github, Ben Bodenmiller Ben Peachey, bookofportals on github, Bruno Baguette, Carlton Gibson, Chris DeLuca, Citizen Esosa, Dan Fandrich, Daniel Brown, Daniel Sabsay, David Piano, DrDoom74 at GitHub, Emil Hessman, enachos71 on github, ethomag on github, Fabian Keil, faterer on github, Frank Dana, Frank Hassanabad, Gautham B A, Geir Hauge, Harry Wright, Helena Udd, Hubert Lin, i-ky on github, infinnovation-dev on GitHub, Jay Ottinger, Jay Satiro, Jeroen Ooms, Johan Wigert, John Simpson, JohnCoconut on github, Jonas Forsberg, Josh Vanderhook, JoyIfBam5, KJM on github, knorr3 on github, lowttl on github, Luca Niccoli, Manuel on github, Marius Žilėnas, Mark Koester, Martin van den Nieuwelaar, mehandes on github, Michael Kaufmann, Ms2ger, Mohammadreza Hendiani, Nick Travers, Nicolas Brassard, Oscar on github, Oskar Köök, Patrik Lundin, RekGRpth on github, Ryan McQuen, Saravanan Musuwathi Kesavan, Senthil Kumaran, Shusen Liu, Sonia Hamilton, Spiros Georgaras, Stephen, Steve Holme, Stian Hvatum, strupo on github, Viktor Szakats, Vitaliy T, Wayne Lai, Wieland Hoffmann, 谭九鼎


This document is licensed under the Creative Commons Attribution 4.0 license.