Features -- what curl can do

curl tool

• config file support

• multiple URLs in a single command line

• range "globbing" support: [0-13], {one,two,three}

• multiple file upload on a single command line

• redirect stderr

• parallel transfers

libcurl

• URL RFC 3986 syntax

• custom maximum download time

• custom lowest download speed acceptable

• custom output result after completion

• guesses protocol from hostname unless specified

• supports .netrc

• progress bar with time statistics while downloading

• standard proxy environment variables support

• have run on 101 operating systems and 28 CPU architectures

• selectable network interface for outgoing traffic

• IPv6 support on Unix and Windows

• happy eyeballs dual-stack IPv4 + IPv6 connects

• persistent connections

• SOCKS 4 + 5 support, with or without local name resolving

• pre-proxy support, for proxy chaining

• supports username and password in proxy environment variables

• operations through HTTP proxy "tunnel" (using CONNECT)

• replaceable memory functions (malloc, free, realloc, etc)

• asynchronous name resolving

• both a push and a pull style interface

• international domain names (IDN)

• transfer rate limiting

• stable API and ABI

• TCP keep alive

• TCP Fast Open

• DNS cache (that can be shared between transfers)

• non-blocking single-threaded parallel transfers

• Unix domain sockets to server or proxy

• DNS-over-HTTPS

• uses non-blocking name resolves

• selectable name resolver backend

URL API

• parses RFC 3986 URLs

• generates URLs from individual components

• manages "redirects"

Header API

• easy access to HTTP response headers, from all contexts

• named headers

• iterate over headers

TLS

• selectable TLS backend(s)

• TLS False Start

• TLS version control

• TLS session resumption

• key pinning

• mutual authentication

• Use dedicated CA cert bundle

• Use OS-provided CA store

• separate TLS options for HTTPS proxy

HTTP

• HTTP/0.9 responses are optionally accepted

• HTTP/1.0

• HTTP/1.1

• HTTP/2, including multiplexing and server push

• GET

• PUT

• HEAD

• POST

• multipart formpost (RFC 1867-style)

• authentication: Basic, Digest, NTLM (9) and Negotiate (SPNEGO) to server and proxy

• resume transfers

• follow redirects

• maximum amount of redirects to follow

• custom HTTP request

• cookie get/send fully parsed

• reads/writes the Netscape cookie file format

• custom headers (replace/remove internally generated headers)

• custom user-agent string

• custom referrer string

• range

• proxy authentication

• time conditions

• via HTTP proxy, HTTPS proxy or SOCKS proxy

• HTTP/2 or HTTP/1.1 to HTTPS proxy

• retrieve file modification date

• Content-Encoding support for deflate, gzip, brotli and zstd

• "Transfer-Encoding: chunked" support in uploads

• HSTS

• alt-svc

• ETags

• HTTP/1.1 trailers, both sending and getting

HTTPS

• HTTP/3

• using client certificates

• verify server certificate

• via HTTP proxy, HTTPS proxy or SOCKS proxy

• select desired encryption

• select usage of a specific TLS version

• ECH

FTP

• download

• authentication

• Kerberos 5

• active/passive using PORT, EPRT, PASV or EPSV

• single file size information (compare to HTTP HEAD)

• 'type=' URL support

• directory listing

• directory listing names-only

• upload

• upload append

• upload via http-proxy as HTTP PUT

• download resume

• upload resume

• custom ftp commands (before and/or after the transfer)

• simple "range" support

• via HTTP proxy, HTTPS proxy or SOCKS proxy

• all operations can be tunneled through proxy

• customizable to retrieve file modification date

• no directory depth limit

FTPS

• implicit ftps:// support that use SSL on both connections

• explicit "AUTH TLS" and "AUTH SSL" usage to "upgrade" plain ftp:// connection to use SSL for both or one of the connections

SSH (both SCP and SFTP)

• selectable SSH backend

• known hosts support

• public key fingerprinting

• both password and public key auth

SFTP

• both password and public key auth

• with custom commands sent before/after the transfer

• directory listing

TFTP

• download

• upload

TELNET

• connection negotiation

• custom telnet options

• stdin/stdout I/O

LDAP

• full LDAP URL support

DICT

• extended DICT URL support

FILE

• URL support

• upload

• resume

SMB

• SMBv1 over TCP and SSL

• download

• upload

• authentication with NTLMv1

SMTP

• authentication: Plain, Login, CRAM-MD5, Digest-MD5, NTLM, Kerberos 5 and External

• send emails

• mail from support

• mail size support

• mail auth support for trusted server-to-server relaying

• multiple recipients

• via http-proxy

SMTPS

• implicit smtps:// support

• explicit "STARTTLS" usage to "upgrade" plain smtp:// connections to use SSL

• via http-proxy

POP3

• authentication: Clear Text, APOP and SASL

• SASL based authentication: Plain, Login, CRAM-MD5, Digest-MD5, NTLM, Kerberos 5 and External

• list emails

• retrieve emails

• enhanced command support for: CAPA, DELE, TOP, STAT, UIDL and NOOP via custom requests

• via http-proxy

POP3S

• implicit pop3s:// support

• explicit STLS usage to "upgrade" plain pop3:// connections to use SSL

• via http-proxy

IMAP

• authentication: Clear Text and SASL

• SASL based authentication: Plain, Login, CRAM-MD5, Digest-MD5, NTLM, Kerberos 5 and External

• list the folders of a mailbox

• select a mailbox with support for verifying the UIDVALIDITY

• fetch emails with support for specifying the UID and SECTION

• upload emails via the append command

• enhanced command support for: EXAMINE, CREATE, DELETE, RENAME, STATUS, STORE, COPY and UID via custom requests

• via http-proxy

IMAPS

• implicit imaps:// support

• explicit "STARTTLS" usage to "upgrade" plain imap:// connections to use SSL

• via http-proxy

MQTT

• Subscribe to and publish topics using URL scheme mqtt://broker/topic