Nginx is an open-source, free; reverse proxy and high-performance HTTP server as well as an IMAP/POP3 proxy server. Its development started in 2002 by Igor Sysoev with the first public release in 2004. Nearly 12.18% (22.2M) of active sites across all domains are hosted by Nginx. It is known for its stability, high performance, rich feature set, low resource consumption, simple configuration.
Nginx is one of a handful of servers that are written for addressing the C10K problem. Nginx doesn't rely on threads for handling requests unlike traditional servers. Rather it uses a more scalable event-driven architecture. This architecture employs small but predictable amounts of memory under load.
Even if you don't expect to handle thousands of simultaneous requests, you can still benefit from Nginx's small memory footprint and high-performance. From the smallest VPS to clusters of servers, Nginx scales in all directions.
Several high-visibility sites are powered by nginx like Hulu, Netflix, Pinterest, Airbnb, CloudFlare WordPress.com, SoundCloud, Zynga, GitHub, Eventbrite, Media Temple, Heroku, RightScale, Zappos, Engine Yard and MaxCDN.
NGINX Inc. also provides consulting services for assisting customers in adding additional features or custom configuration. The support and consulting has been delivered by the original developers and creators of nginx.
Among its various features, the main include the ability of handling more than 10,000 simultaneous connections with a low memory footprint, reverse proxy with caching, auto-indexing, handling of static files, index files, load balancing with in-band health checks, FastCGI, SCGI, uWSGI support with caching, Fault tolerance, name and IP address-based virtual servers, IPv6-compatible, SPDY protocol support, FLV and MP4 streaming, gzip compression and decompression, Web page access authentication, URL rewriting, Response rate, concurrent requests limiting, Bandwidth throttling, Custom logging with on-the-fly gzip compression, WebSockets and HTTP/1.1 Upgrade, OpenSSL, OCSP stapling support, STARTTLS support, TLS/SSL support; POP3, SMTP and IMAP proxy.