nginx

nginx [engine x] is an HTTP and reverse proxy server, a mail proxy server, and a generic TCP/UDP proxy server, originally written by Igor Sysoev. For a long time, it has been running on many heavily loaded Russian sites including Yandex, Mail.Ru, VK, and Rambler. According to Netcraft, nginx served or proxied 20.54% busiest sites in April 2024. Here are some of the success stories: Dropbox, Netflix, Wordpress.com, FastMail.FM.

The sources and documentation are distributed under the 2-clause BSD-like license.

Commercial support is available from Nginx, Inc.

Basic HTTP server features

• Serving static and index files, autoindexing; open file descriptor cache;
• Accelerated reverse proxying with caching; load balancing and fault tolerance;
• Accelerated support with caching of FastCGI, uwsgi, SCGI, and memcached servers; load balancing and fault tolerance;
• Modular architecture. Filters include gzipping, byte ranges, chunked responses, XSLT, SSI, and image transformation filter. Multiple SSI inclusions within a single page can be processed in parallel if they are handled by proxied or FastCGI/uwsgi/SCGI servers;
• SSL and TLS SNI support;
• Support for HTTP/2 with weighted and dependency-based prioritization;
• Support for HTTP/3.

Other HTTP server features

• Name-based and IP-based virtual servers;
• Keep-alive and pipelined connections support;
• Access log formats, buffered log writing, fast log rotation, and syslog logging;
• 3xx-5xx error codes redirection;
• The rewrite module: URI changing using regular expressions;
• Executing different functions depending on the client address;
• Access control based on client IP address, by password (HTTP Basic authentication) and by the result of subrequest;
• Validation of HTTP referer;
• The PUT, DELETE, MKCOL, COPY, and MOVE methods;
• FLV and MP4 streaming;
• Response rate limiting;
• Limiting the number of simultaneous connections or requests coming from one address;
• IP-based geolocation;
• A/B testing;
• Request mirroring;
• Embedded Perl;
• njs scripting language.

Mail proxy server features

• User redirection to IMAP or POP3 server using an external HTTP authentication server;
• User authentication using an external HTTP authentication server and connection redirection to an internal SMTP server;
• Authentication methods:
  • POP3: USER/PASS, APOP, AUTH LOGIN/PLAIN/CRAM-MD5;
  • IMAP: LOGIN, AUTH LOGIN/PLAIN/CRAM-MD5;
  • SMTP: AUTH LOGIN/PLAIN/CRAM-MD5;
• SSL support;
• STARTTLS and STLS support.

TCP/UDP proxy server features

• Generic proxying of TCP and UDP;
• SSL and TLS SNI support for TCP;
• Load balancing and fault tolerance;
• Access control based on client address;
• Executing different functions depending on the client address;
• Limiting the number of simultaneous connections coming from one address;
• Access log formats, buffered log writing, fast log rotation, and syslog logging;
• IP-based geolocation;
• A/B testing;
• njs scripting language.

Architecture and scalability

• One master and several worker processes; worker processes run under an unprivileged user;
• Flexible configuration;
• Reconfiguration and upgrade of an executable without interruption of the client servicing;
• Support for kqueue (FreeBSD 4.1+), epoll (Linux 2.6+), /dev/poll (Solaris 7 11/99+), event ports (Solaris 10), select, and poll;
• The support of the various kqueue features including EV_CLEAR, EV_DISABLE (to temporarily disable events), NOTE_LOWAT, EV_EOF, number of available data, error codes;
• The support of various epoll features including EPOLLRDHUP (Linux 2.6.17+, glibc 2.8+) and EPOLLEXCLUSIVE (Linux 4.5+, glibc 2.24+);
• sendfile (FreeBSD 3.1+, Linux 2.2+, macOS 10.5+), sendfile64 (Linux 2.4.21+), and sendfilev (Solaris 8 7/01+) support;
• File AIO (FreeBSD 4.3+, Linux 2.6.22+);
• DIRECTIO (FreeBSD 4.4+, Linux 2.4+, Solaris 2.6+, macOS);
• Accept-filters (FreeBSD 4.1+, NetBSD 5.0+) and TCP_DEFER_ACCEPT (Linux 2.4+) support;
• 10,000 inactive HTTP keep-alive connections take about 2.5M memory;
• Data copy operations are kept to a minimum.

Tested OS and platforms

• FreeBSD 3 — 12 / i386; FreeBSD 5 — 12 / amd64; FreeBSD 11 / ppc; FreeBSD 12 / ppc64;
• Linux 2.2 — 4 / i386; Linux 2.6 — 5 / amd64; Linux 3 — 4 / armv6l, armv7l, aarch64, ppc64le; Linux 4 — 5 / s390x;
• Solaris 9 / i386, sun4u; Solaris 10 / i386, amd64, sun4v; Solaris 11 / x86;
• AIX 7.1 / powerpc;
• HP-UX 11.31 / ia64;
• macOS / ppc, i386, x86_64;
• Windows XP, Windows Server 2003, Windows 7, Windows 10.