What versions of HTTP exist and which is the most popular in the market?

There are main versions of the HTTP protocol:

• HTTP/0.9 — an very early version, supported only simple GET requests.
• HTTP/1.0 — the first widely used version, supports GET, POST methods, and headers.
• HTTP/1.1 — an improved version with support for persistent connections (keep-alive), chunked transfer, additional methods, and headers. The most common version on the internet.
• HTTP/2 — a modern protocol that improves performance through request multiplexing, header compression, and prioritization.
• HTTP/3 — the latest version based on the QUIC protocol over UDP, providing even faster and more reliable data transfer.

Currently, the most popular version is HTTP/1.1, as it is supported by all browsers and servers. However, HTTP/2 is rapidly gaining popularity and is already widely used, especially for enhancing web application performance. HTTP/3 is in the deployment stage and gradually becoming available.