Nginx (pronounced "engine-x") is free, open-source software that runs on a server and delivers websites. It is known for handling large numbers of simultaneous visitors with little memory, and it is just as often used as a traffic director in front of other applications as it is for serving pages itself.
Why Nginx copes well with many connections
Igor Sysoev released Nginx in 2004 to deal with the problem of serving thousands of connections at once. Instead of giving every visitor its own process or thread, Nginx uses a small number of worker processes that each juggle many connections through an event loop, reacting whenever one has data ready. Slow clients on mobile networks therefore do not tie up a whole worker, which keeps memory use low and predictable under load.
The jobs Nginx is usually given
- Serving static files such as HTML, images, CSS and JavaScript, quickly and with compression.
- Reverse proxy: receiving public requests and passing them to an app running privately, such as Node.js on port 3000.
- TLS termination: handling the HTTPS certificate so the app behind it does not have to.
- Load balancing: spreading requests across several app servers.
- Caching and rate limiting to protect slow backends from repeated or abusive requests.
Example: putting Nginx in front of an app
A developer builds a quoting tool for a roofing company and deploys it on a VPS. The app listens only on the server itself. Nginx listens on ports 80 and 443, redirects HTTP to HTTPS, serves the logo and stylesheets directly, and forwards everything else to the app with a proxy_pass line in a server block. Certbot fetches a free Let's Encrypt certificate and writes the SSL settings into that block.
Nginx compared with Apache
Configuration lives in central files, usually under /etc/nginx/, and there is no per-folder override file like Apache's .htaccess. That makes Nginx faster to evaluate but means changes need server access and a reload. Nginx also does not run PHP itself; it hands PHP requests to a separate PHP-FPM process.
Should you care as a site owner?
Only if you or your developer manage a server. Managed hosts and website platforms may run Nginx under the hood without you ever seeing it. If an error page says "nginx" at the bottom, that is the software reporting a problem, often that the app behind it did not answer (a 502 Bad Gateway).
Typical Nginx mistakes
- Editing config without testing it. Run
nginx -tbefore reloading, or a typo can take every site offline. - Misplaced trailing slashes in proxy rules. A slash on
proxy_passchanges which path the app receives. - Forgetting forwarded headers. Without them, the app sees every visitor as coming from the server itself.
Related terms
- Web server: the category Nginx belongs to.
- Apache: the older main alternative.
- Load balancer: one of the roles Nginx often plays.
- VPS: where people most often install it themselves.