cURL (pronounced like "curl", UK: , US: ) is a computer software project providing a library (libcurl) and command-line tool (curl) for transferring data using various network protocols. The name stands for "Client

URL A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifie ...

History

cURL was first released in 1996. It was originally named ''httpget'' and then became ''urlget'' before adopting the current name of cURL. The original author and lead developer is the Swedish developer Daniel Stenberg, who created cURL because he wanted to automate the fetching of currency exchange rates for IRC users.

libcurl

libcurl is a free client-side URL transfer library, supporting

cookie A cookie is a baked or cooked snack or dessert that is typically small, flat and sweet. It usually contains flour, sugar, egg, and some type of oil, fat, or butter. It may include other ingredients such as raisins, oats, chocolate chips, n ...

s, DICT, FTP, FTPS, Gopher, HTTP/1 (with HTTP/2 and

HTTP/3 HTTP/3 is the third major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web, complementing the widely-deployed HTTP/1.1 and HTTP/2. Unlike previous versions which relied on the well-established TCP ( ...

support), HTTP POST,

HTTP PUT The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, w ...

, HTTP proxy tunneling, HTTPS, IMAP, Kerberos, LDAP, MQTT, POP3, RTSP, RTMP,

SCP SCP may refer to: Organizations Political parties * Soviet Communist Party, the leading political party in the former Soviet Union * Syrian Communist Party * Sudanese Communist Party * Scottish Christian Party Companies * Seattle Computer Produ ...

, SMTP, and SMB. The library supports the file URI scheme, SFTP, Telnet, TFTP, file transfer resume, FTP uploading, HTTP form-based upload, HTTPS certificates, LDAPS, proxies, and user-plus-password authentication. The libcurl library is portable. It builds and works identically on many platforms, including

AIX Aix or AIX may refer to: Computing * AIX, a line of IBM computer operating systems *An Alternate Index, for a Virtual Storage Access Method Key Sequenced Data Set *Athens Internet Exchange, a European Internet exchange point Places Belgium ...

, AmigaOS,

Android Android may refer to: Science and technology * Android (robot), a humanoid robot or synthetic organism designed to imitate a human * Android (operating system), Google's mobile operating system ** Bugdroid, a Google mascot sometimes referred to ...

BeOS BeOS is an operating system for personal computers first developed by Be Inc. in 1990. It was first written to run on BeBox hardware. BeOS was positioned as a multimedia platform that could be used by a substantial population of desktop users a ...

BlackBerry Tablet OS BlackBerry Tablet OS is an operating system from BlackBerry Ltd based on the QNX Neutrino real-time operating system designed to run Adobe AIR and BlackBerry WebWorks applications, currently available for the BlackBerry PlayBook tablet computer ...

and BlackBerry 10,

OpenVMS OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...

Darwin Darwin may refer to: Common meanings * Charles Darwin (1809–1882), English naturalist and writer, best known as the originator of the theory of biological evolution by natural selection * Darwin, Northern Territory, a territorial capital city i ...

, DOS,

FreeBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...

HP-UX HP-UX (from "Hewlett Packard Unix") is Hewlett Packard Enterprise's proprietary implementation of the Unix operating system, based on Unix System V (initially System III) and first released in 1984. Current versions support HPE Integrity Ser ...

, HURD, iOS,

IRIX IRIX ( ) is a discontinued operating system developed by Silicon Graphics (SGI) to run on the company's proprietary MIPS workstations and servers. It is based on UNIX System V with BSD extensions. In IRIX, SGI originated the XFS file system and ...

, Linux, macOS,

NetBSD NetBSD is a free and open-source Unix operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is a ...

NetWare NetWare is a discontinued computer network operating system developed by Novell, Inc. It initially used cooperative multitasking to run various services on a personal computer, using the IPX network protocol. The original NetWare product in 19 ...

OpenBSD OpenBSD is a security-focused, free and open-source, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by forking NetBSD 1.0. According to the website, the OpenBSD project em ...

, OS/2, QNX Neutrino, RISC OS,

Solaris Solaris may refer to: Arts and entertainment Literature, television and film * ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem ** ''Solaris'' (1968 film), directed by Boris Nirenburg ** ''Solaris'' (1972 film), directed by ...

Symbian Symbian is a discontinued mobile operating system A mobile operating system is an operating system for mobile phones, tablets, smartwatches, smartglasses, or other non-laptop personal mobile computing devices. While computers such as typic ...

, Tru64,

Ultrix Ultrix (officially all-caps ULTRIX) is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations. History The initial development of Unix occurred on DEC equip ...

, UnixWare, and

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

. The libcurl library is free, thread-safe and IPv6 compatible. Bindings are available for more than 50

languages Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...

, including C/ C++, Java, PHP and Python. The libcurl library supports GnuTLS, mbed TLS, NSS, gskit on

IBM i IBM i (the ''i'' standing for ''integrated'') is an operating system developed by IBM for IBM Power Systems. It was originally released in 1988 as OS/400, as the sole operating system of the IBM AS/400 line of systems. It was renamed to i5/OS in ...

, SChannel on Windows,

Secure Transport The Transport Layer Security (TLS) protocol provides the ability to secure communications across networks. This comparison of TLS implementations compares several of the most notable libraries. There are several TLS implementations which are free ...

on macOS and iOS,

SSL/TLS Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securi ...

through

OpenSSL OpenSSL is a software library for applications that provide secure communications over computer networks against eavesdropping or need to identify the party at the other end. It is widely used by Internet servers, including the majority of HTT ...

Boringssl OpenSSL is a software library for applications that provide secure communications over computer networks against eavesdropping or need to identify the party at the other end. It is widely used by Internet servers, including the majority of HTT ...

, libressl, AmiSSL, wolfSSL, BearSSL and rustls.

curl

curl is a command-line tool for getting or sending data including files using

syntax. Since curl uses libcurl, it supports every protocol libcurl supports. curl supports HTTPS and performs SSL certificate verification by default when a secure protocol is specified such as HTTPS. When curl connects to a remote server via HTTPS, it will obtain the remote server certificate, then check against its

CA certificate In cryptography, a certificate authority or certification authority (CA) is an entity that stores, signs, and issues digital certificates. A digital certificate certifies the ownership of a public key by the named subject of the certificate. This ...

store the validity of the remote server to ensure the remote server is the one it claims to be. Some curl packages are bundled with CA certificate store file. There are several options to specify a CA certificate such as and . The option can be used to specify the location of the CA certificate store file. In the Windows platform, if a CA certificate file is not specified, curl will look for a CA certificate file name “curl-ca-bundle.crt” in the following order: # Directory where the curl program is located. # Current working directory. # Windows system directory. # Windows directory. # Directories specified in the %PATH% environment variables. curl 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. or 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.

Examples

Basic use of curl involves simply typing at the command line, followed by the URL of the output to retrieve: $ curl www.example.com curl defaults to displaying the output it retrieves to the standard output specified on the system (usually the terminal window). So running the command above would, on most systems, display the www.example.com source-code in the terminal window. The -o flag can be used to store the output in a file instead: $ curl -o example.html www.example.com More options that change the tool's behavior are available.

References

External links