Search code, repositories, users, issues, pull requests...
As you may have heard, after 4 years of work, the new HTTP/3 and QUIC protocols are finally approaching official standardization. Preview versions are now available for testing in servers and browsers alike.
HTTP/3 is promising major performance improvements compared to HTTP/2, mainly because it changes its underlying transport protocol from TCP to QUIC over UDP. In this post, we'll be taking an in-depth look at just one of these improvements, namely the removal of the "Head-of-Line blocking" (HOL blocking) problem. This is useful because I've read a lot of misconceptions on what this actually means and how much it helps in practice. Solving HOL blocking was also one of the main motivations behind not just HTTP/3 and QUIC but also HTTP/2, so it gives a fantastic insight in the reasons for protocol evolution as well.
I'll first introduce the problem and then track different forms of it throughout HTTP's history. We will also look how it interacts with other systems like prioritization and congestion control. The goal is to help people make correct assumptions about HTTP/3's performance improvements, which (spoiler) might not be as amazing as sometimes claimed in marketing materials.
