CURL is a command-line tool used to transfer data over the Internet. It is maintained by thousands of contributors and sponsors worldwide and is free and open-source software, following established open-source best practices.
In terms of main capabilities, the protocols supported by CURL include DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, MQTTS, POP3, POP3S, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS, WSS. Proxy support includes SOCKS4, SOCKS5, HTTP, HTTPS (HTTP/1 and HTTP/2), tunneling, unix domain sockets, haproxy, SOCKS+HTTP proxy chaining. HTTP methods support GET, POST, PUT, HEAD, multipart formpost, as well as HTTP/0.9, HTTP/1.0, HTTP/1.1, HTTP/2 (h2c, h2, prior knowledge), HTTP/3 (dual connect h1/h2 + h3 or h3-only), and support HSTS, Alt-Svc, cookies, PSL, etags, transfer compression, ranges, custom headers, custom methods, follow redirects. For FTP, it supports IPv6 (EPRT, EPSV), STLS, upload/download, append, range, passive/active mode, kerberos, directory listing, custom commands. SCP and SFTP support known hosts, md5/sha256 fingerprints, compression, upload/download, directory listing. TLS supports 1.0 to 1.3, mutual authentication, STARTTLS, OCSP stapling, ECH, False Start, key pinning, PQC ready, session resumption, early data, session export/import. QUIC supports 0RTT handshake. Authentication methods support Basic, Plain, Digest, CRAM-MD5, SCRAM-SHA, NTLM, Negotiate, Kerberos, Bearer tokens, AWS Sigv4, SASL, .netrc. HTTP compression supports gzip, brotli, and zstd. Name resolution supports DNS-over-HTTPS, custom addresses for host, name+port redirect, custom DNS servers, DNS cache, HTTPS RR. Connections support connection reuse, interface binding, Happy Eyeballs, IPv4/IPv6 only, unix domain sockets, TCP keepalive, TCP Fast Open, TCP Nodelay, MPTCP, VLAN priority, IP Type Of Service. Transfers support transfer rate limiting, request rate limiting, stall detection, retries, timeouts. URLs support an unlimited number, parallel and serial transfers, globbing. Output supports IDN hostnames, custom transfer information, JSON-formatted metadata, by content-disposition, libcurl source code, bold headers.
In terms of usage, CURL is a command-line tool invoked through command-line arguments; its code is available on GitHub.
In terms of applicable scenarios, CURL is used daily by almost everyone using the Internet worldwide and can be used for data transfer and debugging across various protocols.
In terms of limitations, the materials do not provide specific installation commands, platform support lists, charging or pricing information, usage steps, or performance data; this content is not provided for now. The latest stable version is 8.22.0, released on 2026-09-02.
