If you are installing NGINX using an apt package manager like
apt install nginx-full
You will install nginx 1.18 despite using the latest Ubuntu (Ubuntu 22.04) and yet still use HTTP 1.1 on the default nginx vhost SSL configuration.
So, in order to use HTTP/2, you should change the line listen ssl to
listen ssl http2.
listen [::]:443 ssl ipv6only=on; # managed by Certbot listen 443 ssl; # managed by Certbot
listen [::]:443 ssl ipv6only=on http2; # managed by Certbot listen 443 ssl http2; # managed by Certbot
What is the HTTP/2 Protocol
HTTP/2 improved on HTTP/1.1 in a number of ways that allowed for speedier content delivery and improved user experience, including:
- Binary protocols – Binary protocols consume less bandwidth, are more efficiently parsed, and are less error-prone than the textual protocols used by HTTP/1.1. Additionally, they can better handle elements such as whitespace, capitalization, and line endings.
- Multiplexing – HTTP/2 is multiplexed, i.e., it can initiate multiple requests in parallel over a single TCP connection. As a result, web pages containing several elements are delivered over one TCP connection. These capabilities solve the head-of-line blocking problem in HTTP/1.1, in which a packet at the front of the line blocks others from being transmitted.
- Header compression – HTTP/2 uses header compression to reduce the overhead caused by TCP’s slow-start mechanism.
- Server push – HTTP/2 servers push likely-to-be-used resources into a browser’s cache, even before they’re requested. This allows browsers to display content without additional request cycles.
- Increased security – Web browsers only support HTTP/2 via encrypted connections, increasing user and application security.
HTTP/2 explanation : https://www.imperva.com/learn/performance/http2/