curl/docs/FEATURES.md

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
• custom maximum transfer rate
• redirectable stderr
• metalink support (13)
• parallel transfers

libcurl

• full URL syntax with no length limit
• custom maximum download time
• custom least download speed acceptable
• custom output result after completion
• guesses protocol from host name unless specified
• uses .netrc
• progress bar with time statistics while downloading
• "standard" proxy environment variables support
• compiles on win32 (reported builds on 70+ operating systems)
• selectable network interface for outgoing traffic
• IPv6 support on unix and Windows
• happy eyeballs dual-stack connects
• persistent connections
• SOCKS 4 + 5 support, with or without local name resolving
• supports user name and password in proxy environment variables
• operations through HTTP proxy "tunnel" (using CONNECT)
• replaceable memory functions (malloc, free, realloc, etc)
• asynchronous name resolving (6)
• both a push and a pull style interface
• international domain names (11)

HTTP

• HTTP/0.9 responses are optionally accepted
• HTTP/1.0
• HTTP/1.1
• HTTP/2, including multiplexing and server push (5)
• GET
• PUT
• HEAD
• POST
• multipart formpost (RFC1867-style)
• authentication: Basic, Digest, NTLM (9) and Negotiate (SPNEGO) (3) to server and proxy
• resume (both GET and PUT)
• 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
• retrieve file modification date
• Content-Encoding support for deflate and gzip
• "Transfer-Encoding: chunked" support in uploads
• automatic data compression (12)

HTTPS (1)

• (all the HTTP features)
• HTTP/3 experimental support
• using client certificates
• verify server certificate
• via HTTP proxy, HTTPS proxy or SOCKS proxy
• select desired encryption
• select usage of a specific SSL version

FTP

• download
• authentication
• Kerberos 5 (14)
• active/passive using PORT, EPRT, PASV or EPSV
• single file size information (compare to HTTP HEAD)
• 'type=' URL support
• dir listing
• dir 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 dir depth limit

FTPS (1)

• 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

SCP (8)

• both password and public key auth

SFTP (7)

• both password and public key auth
• with custom commands sent before/after the transfer

TFTP

• download
• upload

TELNET

• connection negotiation
• custom telnet options
• stdin/stdout I/O

LDAP (2)

• 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 (9), Kerberos 5 (4) and External.
• send e-mails
• mail from support
• mail size support
• mail auth support for trusted server-to-server relaying
• multiple recipients
• via http-proxy

SMTPS (1)

• 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 (9), Kerberos 5 (4) and External.
• list e-mails
• retrieve e-mails
• enhanced command support for: CAPA, DELE, TOP, STAT, UIDL and NOOP via custom requests
• via http-proxy

POP3S (1)

• 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 (9), Kerberos 5 (4) and External.
• list the folders of a mailbox
• select a mailbox with support for verifying the UIDVALIDITY
• fetch e-mails with support for specifying the UID and SECTION
• upload e-mails via the append command
• enhanced command support for: EXAMINE, CREATE, DELETE, RENAME, STATUS, STORE, COPY and UID via custom requests
• via http-proxy

IMAPS (1)

• 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

Footnotes

1. requires a TLS library
2. requires OpenLDAP or WinLDAP
3. requires a GSS-API implementation (such as Heimdal or MIT Kerberos) or SSPI (native Windows)
4. requires a GSS-API implementation, however, only Windows SSPI is currently supported
5. requires nghttp2
6. requires c-ares
7. requires libssh2, libssh or wolfSSH
8. requires libssh2 or libssh
9. requires OpenSSL, GnuTLS, mbedTLS, NSS, yassl, Secure Transport or SSPI (native Windows)
10. -
11. requires libidn2 or Windows
12. requires libz, brotli and/or zstd
13. requires libmetalink, and either an Apple or Microsoft operating system, or OpenSSL, or GnuTLS, or NSS
14. requires a GSS-API implementation (such as Heimdal or MIT Kerberos)