Which RFCs are worth reading for web development?

RFC 9111 on HTTP caching would be my next pick. It covers freshness, Cache-Control, validators such as ETag, and revalidation. That stuff pays off when you're trying to work out why an asset or response is stale.

You may see older recommendations for RFC 7234. RFC 9111 replaced it, so start with the newer document.

For cookies, read RFC 6265. It gets into the details of how cookies are stored and sent, including some behavior that can feel pretty odd from an application developer's point of view.

Also check the current status of the 6265bis work for newer cookie behavior, including SameSite. Don't assume the older RFC alone describes everything a modern browser does.

I'd go through the HTTP version documents alongside 9110 rather than trying to memorize them all at once. RFC 9112 covers HTTP/1.1 message syntax and routing. RFC 9113 covers HTTP/2, including binary framing and multiplexed streams. RFC 9114 covers HTTP/3 over QUIC.

Pick a question first, like how a message is framed or how multiple requests share a connection, then compare the relevant sections. The versions share semantics, but their transport details differ.

RFC 3986 is a good foundation for URI syntax. It gives you a vocabulary for the components and grammar instead of treating every URL as one big string. Useful background for thinking about paths, queries, and routing.

For authentication-related work, add RFC 6749 on OAuth 2.0. It's useful for understanding the roles and flows behind authorization rather than treating the whole thing as a mysterious redirect.

I'd also keep MIME and BCP 47 for language tags on the reading list if you work with content types or localization. They may not be the first stop for every project, but they give useful context for content negotiation.