View source for CURL

{{Short description|Free URL data transfer client software}}
{{confused|Curl (programming language)}}
{{Other uses|Curl (disambiguation){{!}}Curl}}
{{lowercase title}}
{{Infobox software
| name = curl
| logo = Curl-logo.svg
| author = [[Daniel Stenberg]]<ref name=17yearhistory />
| developer = [https://curl.se/docs/thanks.html Contributors to the curl project]
| released = {{Start date and age|1996}}<ref name=history />
| latest release version = {{wikidata|property|preferred|reference|edit|Q286306|P348|P548=Q2804309}}
| latest release date = {{wikidata|qualifier|preferred|single|Q286306|P348|P548=Q2804309|P577}}
| latest preview version = {{wikidata|property|preferred|reference|edit|Q286306|P348|P548=Q51930650}}
| latest preview date = {{wikidata|qualifier|preferred|single|Q286306|P348|P548=Q51930650|P577}}
| programming language = [[C (programming language)|C]]
| platform = 29 platforms (see {{section link || libcurl}} for details)
| genre = [[Web client]] (supports e.g. [[HTTPS]], and [[FTP client|FTP]])
| license = curl license<ref name="spdx">{{cite web|url=https://spdx.org/licenses/curl.html|title=curl License|website=spdx.org}}</ref><ref name="license">{{cite web|url=https://curl.se/docs/copyright.html|title=curl - copyright|website=curl.se|access-date=2024-01-17|url-status=live|archive-url=https://web.archive.org/web/20240115151446/https://curl.se/docs/copyright.html|archive-date=2024-01-15}}</ref> (inspired by the [[MIT License]]<ref name="license"/>) and a fraction uses the [[ISC license|ISC]]
}}
'''cURL''' (pronounced like "curl",<ref name = "FAQ, haxx.se" /> {{IPAc-en|k|ɜːr|l}}) is a [[Free and open-source software|free and open source]] [[Command-line interface|CLI]] app for [[uploading]] and [[downloading]] individual files. It can download a [[URL]] from a [[web server]] over [[HTTP]], and supports a variety of other [[Application layer|network protocols]], [[Uniform Resource Identifier|URI]] schemes, multiple versions of HTTP, and [[Proxy server|proxying]]. The project consists of a [[library (computing)|library]] ('''libcurl''') and [[command-line tool]] ('''curl'''), which have been widely ported to different [[Computing platform|computing platforms]]. It was created by [[Daniel Stenberg]], who is still the lead developer of the project.

==History==
The software was first released in 1996,<ref name="RelFirst">{{cite web |title=History of curl |url=https://curl.se/docs/history.html |url-status=live |archive-url=https://web.archive.org/web/20210917071434/https://curl.se/docs/history.html |archive-date=September 17, 2021 |access-date=May 11, 2021 |publisher=fossies.org |language=en-US}} </ref> originally named <code>httpget</code> and then became <code>urlget</code>, before adopting the current name of <code>curl</code>.<ref name = "cURL changelog, 2020" /><ref name = "Stenberg, Haxx SE, 2020" /> The name stands for "Client for [[URL]]".<ref name="Stenberg, haxx.se, 2018" /> The original author and lead developer is the Swedish developer [[Daniel Stenberg]], who created curl to power part of an [[IRC bot]], because he wanted to automatically provide currency exchange rates, fetched from a website, to users in an [[Internet_Relay_Chat|IRC]] [[chat room]].<ref name=history/>

== Components ==

=== libcurl ===
<code>libcurl</code> is a client-side URL transfer [[Library (computing)|library]] that powers <code>curl</code>.<ref name="BlueOne" /> It supports numerous internet protocols including [[DICT]], [[file URI scheme|FILE]], [[FTP]], [[FTPS]], [[Gopher (protocol)|GOPHER]], [[GOPHERS]], [[HTTP]], [[HTTPS]], [[IMAP]], [[IMAPS]], [[LDAP]], [[LDAPS]], [[MQTT]], [[POP3]], [[POP3S]], [[Real-Time_Messaging_Protocol|RTMP]], [[RTMPS]], [[RTSP]], [[Secure copy protocol|SCP]], [[SSH File Transfer Protocol|SFTP]], [[Server Message Block|SMB]], [[Server Message Block#SMB_3.1.1|SMBS]], [[SMTP]], [[SMTPS]], [[TELNET]], [[Trivial File Transfer Protocol|TFTP]], [[WebSocket|WS]] and [[WebSocket|WSS]].

libcurl supports [[HTTP]] versions 0.9, 1.0, 1.1, [[HTTP/2]] and [[HTTP/3]] including h2c, prior-knowledge, dual-connect modes, and [[QUIC]] with 0-RTT handshakes.

The library provides features such as [[cookie (web)|cookie]] handling, standard HTTP request methods ([[HTTP_GET|GET]], [[POST_(HTTP)|POST]], [[HTTP_PUT|PUT]], [[HTTP_HEAD|HEAD]], multipart form uploads), and authentication mechanisms including Basic, Digest, [[NTLM]], Negotiate, [[CRAM-MD5]], SCRAM-SHA, Kerberos, Bearer tokens, AWS Sigv4, [[Simple_Authentication_and_Security_Layer|SASL]], and reading credentials from .netrc.

<code>libcurl</code> supports a variety of security and transport features, including [[Transport_Layer_Security|TLS]] [[TLS_1.0|1.0]]-[[TLS_1.3|1.3]], mutual authentication, [[Opportunistic_TLS|STARTTLS]], [[OCSP stapling]], [[Encrypted Client Hello]] ([[Encrypted Client Hello|ECH]]), False Start, key pinning, [[Post-quantum_cryptography|post-quantum]] readiness, session resumption, early data, session import/export, [[HTTP_Strict_Transport_Security|HSTS]], Alt-Svc, [[Public Suffix List]] ([[Public Suffix List|PSL]]), [[HTTP_ETag|entity tags]] ([[HTTP_ETag|ETags]]), range requests, transfer compression ([[gzip]], [[Brotli]], [[zstd]]), custom headers, custom methods, and redirect following.

It also offers proxy and networking support, including [[SOCKS4]], [[SOCKS5]], [[HAProxy]], and [[HTTP proxy|HTTP proxies]] with chaining and [[Unix domain sockets]], as well as user-plus-password authentication<ref name=curl1>{{cite web |title=curl - How To Use |url=https://curl.se/docs/manpage.html |website=curl.se}}</ref>. Advanced name-resolution features include [[DNS-over-HTTPS]], custom [[DNS]] servers, host/port mappings, and DNS caching.

Additional functionality includes file transfer resume, [[FTP]] uploading, form-based [[HTTP]] upload, [[HTTPS]] certificates, and mechanisms for controlling and monitoring transfers such as configurable timeouts, automatic retries, rate limiting, and detection of stalled connections. The library also provides enhanced reporting features, including JSON-formatted metadata, content-disposition handling, [[Internationalized_domain_name|IDN]] hostname display, and customizable transfer information.

The <code>libcurl</code> library is portable, as it builds and works identically on most platforms, including:<ref>{{cite web |title=Third-party open-source software Curl |url=https://gitee.com/openharmony/third_party_curl |website=Gitee |publisher=OpenAtom OpenHarmony |access-date=17 March 2024}}</ref><ref>{{cite web |title=Third-party open-source software Curl |url=https://github.com/openharmony/third_party_curl |website=GitHub |publisher=OpenAtom OpenHarmony |access-date=17 March 2024}}</ref><ref name = "Windows Command Line blog" />
{{div col|colwidth=10em}}
* [[AIX]]
* [[AmigaOS]]
* [[Android (operating system)|Android]]{{Citation needed|date=April 2022}}
* [[Azure_Sphere|Azure Sphere OS]]
* [[BeOS]]
* [[BlackBerry Tablet OS]] and [[BlackBerry 10]]<ref name = "Blackberry, GitHub" />
* Cesium
* [[Darwin (operating system)|Darwin]]
* [[DOS]]
* [[Deos]]
* [[FreeBSD]]
* [[FreeRTOS]]
* [[HP-UX]]
* [[HURD]]
* [[iOS]]
* [[IRIX]]
* [[Linux]]
* [[macOS]]
* [[NetBSD]]
* [[NetWare]]
* [[OpenBSD]]
* [[OpenHarmony]]
* [[OpenVMS]]
* [[OS/2]]
* [[QNX]]
* [[QNX Neutrino]]
* [[RISC OS]]
* [[RTEMS]]
* [[Solaris (operating system)|Solaris]]
* [[Symbian]]
* [[Tru64]]
* [[Ultrix]]
* [[UnixWare]]
* [[Windows]]
* [[VxWorks]]
* [[Zephyr_(operating system)|Zephyr]]
{{div col end}}

The <code>libcurl</code> library is [[thread-safe]] and [[IPv6]] compatible. [[Language binding|Bindings]] are available for more than 50 [[computer languages|languages]], including [[C (programming language)|C]], [[C++]], [[Java (programming language)|Java]], [[Julia (programming language)|Julia]] (is bundled with), [[PHP]] and [[Python (programming language)|Python]].<ref>{{cite web|url=https://curl.se/libcurl/bindings.html|title=libcurl bindings|publisher=curl.se}}</ref>

The <code>libcurl</code> library supports [[Transport Layer Security|SSL/TLS]] through [[GnuTLS]], [[mbedTLS]], [[Security Support Provider Interface|SChannel]] (on Windows), [[OpenSSL]], [[BoringSSL]], [[AWS-LC]], [[QuicTLS]], [[LibreSSL]], [[AmiSSL]], [[wolfSSL]] and {{proper name|[[rustls]]}}.<ref>{{Cite web|title=curl supports rustls {{!}} daniel.haxx.se|date=9 February 2021 |url=https://daniel.haxx.se/blog/2021/02/09/curl-supports-rustls/|access-date=2022-01-01|language=en-US}}</ref>

=== curl ===
<code>curl</code> is a command-line tool for getting or sending data, including files, using [[URL]] syntax. <code>curl</code> provides an interface to the <code>libcurl</code> library; it supports every protocol <code>libcurl</code> supports.<ref name=curl1/>

<code>curl</code> supports [[HTTPS]], and performs SSL or TLS certificate verification by default.  When <code>curl</code> connects to a remote server via HTTPS, it will obtain the remote server certificate, then checks against its [[CA certificate]] store the validity of the remote server to ensure the remote server is the one it claims to be.  Some <code>curl</code> packages are bundled with a CA certificate store file.  There are several options to specify a CA certificate, such as <code>--cacert</code> and <code>--capath</code>. The <code>--cacert</code> option can be used to specify the location of the CA certificate store file.

Starting with Windows 10 version 1809, Windows ships with <code>curl.exe</code>.<ref name = "Windows Command Line blog"  /> On Microsoft Windows, if a CA certificate file is not specified, curl will look for the <code>curl-ca-bundle.crt</code> file in the following locations, in the order given:<ref name="SSL, haxx.se" />
# App's folder (where <code>curl.exe</code> is located)
# Current working directory
# <code>C:\Windows\System32</code> directory
# <code>C:\Windows</code> directory
# Directories specified in the [[PATH (variable)|<code>PATH</code>]] environment variable

<code>curl</code> will return an error message if the remote server is using a self-signed certificate, or if the remote server certificate is not signed by a CA listed in the CA cert file. <code>-k</code> or <code>--insecure</code> option can be used to skip certificate verification. Alternatively, if the remote server is trusted, the remote server CA certificate can be added to the CA certificate store file.

===tiny-curl===
<code>tiny-curl</code> is a lightweight version of libcurl developed by wolfSSL Inc. for embedded and resource-constrained devices. It implements HTTPS functionality in roughly 100 KB of code on typical 32-bit architectures.

==Licensing==
curl and libcurl are distributed under the MIT License. tiny-curl, a version of curl optimized for embedded systems and supported by wolfSSL, is available under both the [[GNU General Public License|GNU GPLv3-or-later]] and commercial licensing.

Rock-solid curl<ref>{{Cite web |url=https://rock-solid.curl.dev/ |title=Rock-solid curl}}</ref>, the long-term support (LTS) edition, uses the same curl license by default, with an option for commercial licensing for organizations that require contractual support or warranty coverage.

==See also==
{{Portal|Free and open-source software}}
* [[curl-loader]] – an open-source testing tool based on curl
* [[libwww]] – an early library that comes with a command line interface
* [[PowerShell]] – the ''iwr'' (Invoke-WebRequest) Windows PowerShell had functionality similar to curl; class Web-client too.<ref name = "Ryan, Ryandel, 2018" />
* [[Web crawler]] – an internet bot that can crawl the web
* [[Wget]] – similar command-line tool with no associated library but capable of recursive downloading

==References==
{{Reflist|2|refs=
<ref name=17yearhistory>{{cite web |url=https://daniel.haxx.se/blog/2015/03/20/curl-17-years-old-today/ |title=curl, 17 years old today |last1=Stenberg |first1=Daniel |date=20 March 2015 |website=daniel.haxx.se |access-date=20 March 2015}}</ref>
<ref name=history>{{cite web |url=https://curl.se/docs/history.html |title=History of curl - How curl Became Like This |publisher=curl |access-date=November 17, 2016 |quote=Daniel simply adopted an existing command-line open-source tool, httpget, that Brazilian Rafael Sagula had written and recently release 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. [...] 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. |archive-url=https://web.archive.org/web/20170930163727/https://curl.se/docs/history.html |archive-date=September 30, 2017 |url-status=dead }}</ref>
<ref name = "FAQ, haxx.se" >{{Cite web|url=https://curl.se/docs/faq.html|title=curl - Frequently Asked Questions|website=curl.se}}</ref>
<ref name = "Stenberg, haxx.se, 2018" >{{Cite web|url=https://everything.curl.dev/project/name|title=Origin of the name|last=Stenberg|first=Daniel|website=curl.se|language=en|access-date=2021-03-27}}</ref>
<ref name="BlueOne">{{cite web|title=Conversing through the Internet with cURL and libcurl - Using libcurl with C and Python|url=https://www.ibm.com/developerworks/library/os-curl/index.html|website=IBM Developerworks|access-date=12 September 2018|first=M. Tim|last=Jones|date=8 September 2009|url-status=live|archive-date=14 April 2015|archive-url=https://web.archive.org/web/20150414143804/https://www.ibm.com/developerworks/library/os-curl/index.html|df=dmy-all}}</ref>
<ref name = "Blackberry, GitHub" >{{Cite web |url=https://blackberry.github.com/ndk/components.html |title=Open Source Components for the Native SDK for BlackBerry Tablet OS |access-date=2017-09-19 |archive-url=https://web.archive.org/web/20130127102233/http://blackberry.github.com/ndk/components.html |archive-date=2013-01-27 |url-status=dead }}</ref>
<ref name = "Windows Command Line blog" >{{Cite web |first=Rich |last=Turner |url=https://devblogs.microsoft.com/commandline/tar-and-curl-come-to-windows/ |title=Tar and Curl Come to Windows! |date=18 January 2018 |website=Windows Command Line |publisher=[[Microsoft]]}}</ref>
<ref name = "SSL, haxx.se" >{{Cite web|url=https://curl.se/docs/sslcerts.html|title=curl - SSL CA Certificates|website=curl.se}}</ref>
<ref name = "cURL changelog, 2020" > {{ Cite web | url = https://curl.se/changes.html#4_0 | title = Changelog | access-date = 2020-01-04 | date = 2020-01-04 | quote = The first curl release. The tool was named urlget before this. And httpget before that.  | language = en | df = dmy-all }} </ref>
<ref name = "Stenberg, Haxx SE, 2020" > {{ Cite web | url = https://daniel.haxx.se/blog/2020/01/04/restored-complete-curl-changelog/ | title = Restored complete curl changelog | access-date = 2020-01-02 | first = Daniel | last = Stenberg | author-link = Daniel Stenberg | date = 2020-01-04 | website = Haxx Se | format = html | df = dmy-all }} </ref>
<ref name = "Ryan, Ryandel, 2018" > {{ Cite web | url = https://www.ryadel.com/curl-wget-comandi-equivalenti-alternative-windows-command-line-prompt-powershell/
 | title = Comandi equivalenti a cURL e Wget per Windows command-line con Powershell | access-date = 2020-01-04 | first = Ryan | date = 2018-03-02 | website = Ryadel | language = it | trans-title = cURL and Wget equivalent commands for Windows command-line with Powershell | quote = Per emulare il comportamento del comando Linux  cURL, è sufficiente creare un file cURL.ps1 contenente la seguente riga di codice | format = html | df = dmy-all | last = Del }} </ref>
}}

==External links==
{{Wikibooks|Guide to Windows Commands}}
* {{official website}}

{{Download managers}}
{{Windows commands}}

{{DEFAULTSORT:Curl}}
[[Category:1997 software]]
[[Category:C (programming language) libraries]]
[[Category:Command-line software]]
[[Category:Cross-platform free software]]
[[Category:Download managers]]
[[Category:Free FTP clients]]
[[Category:Free software programmed in C]]
[[Category:Free web crawlers]]
[[Category:Hypertext Transfer Protocol clients]]
[[Category:Software using the MIT license]]
[[Category:Telnet]]
[[Category:Web scraping]]