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