Enable HTTP/2 on Nginx

HTTP/2 carries many streams on one connection and compresses headers with HPACK, where HTTP/1.1 usually queues requests on each connection so a page full of files waits its turn. Multiplexing is the change. It is not a faster disk and not a new bandwidth cap.

Nginx cuts the response into chunks; the default http2_chunk_size is 8k. A much smaller chunk adds overhead, and a much larger chunk weakens prioritization because of head-of-line blocking inside the stream — leave 8k unless you have measured a reason to move it. One large file still moves at the speed of the link: the protocol helps when the browser asks for CSS, JavaScript and images together. If the wait is PHP or the database, start with why a website is slow. The edit itself needs root, which VPS hosting includes and shared hosting does not.

On Nginx 1.25.1 and newer the switch is the http2 directive: it appeared in that version, defaults to off, and is valid in the http and server contexts. The module page's example is listen 443 ssl; followed by http2 on; plus the certificate lines.

listen 443 ssl;
listen [::]:443 ssl;
http2 on;

Put those lines in the server block that already has the certificate. Omit the IPv6 listen line if this host has no IPv6 listener, and leave the existing ssl_certificate and ssl_certificate_key lines where they are.

Before 1.25.1, published steps put the flag on the listen line, and older guides — a June 2022 community thread and an SSL vendor's steps among them — still show that form. Use the form that matches nginx -v, and read the warning from nginx -t instead of stacking both forms. A proxy in front can also speak HTTP/1.1 to your origin while the browser uses HTTP/2 to the proxy, so confirm the hop you actually control.

1. Copy the file you will edit. On a VPS it is often under /etc/nginx/sites-available/ or /etc/nginx/conf.d/, not always the main nginx.conf.
2. Add the version-correct lines in the server block that already holds the certificate, mirroring them on the IPv6 listen line when that line exists.
3. Run nginx -t. Fix the path it names; a failed test leaves the running config untouched.
4. Reload with systemctl reload nginx. A reload is enough — a full restart is not required for this change.
5. If nginx -t names a file you cannot place, email support@webji.services; the mailbox is 24/7 in Hindi and English, and the office phone is not a support line.

Do not enable server push as part of turning HTTP/2 on: http2_push, http2_push_preload and http2_max_concurrent_pushes have been obsolete since Nginx 1.25.1, and the module page names early_hints as the replacement for push. What was worth tuning instead moved to core directives in 1.19.7.

• keepalive_timeout replaces http2_idle_timeout.
• keepalive_requests replaces http2_max_requests.
• large_client_header_buffers replaces http2_max_field_size and http2_max_header_size.
• client_header_timeout replaces http2_recv_timeout.