The modern Web - Good explanation of web networking.
WireMock - Tool for mocking HTTP services.
llhttp - Port of http_parser to llparse.
see - Static web server, developed using rust.
serve-dir - "python -m SimpleHTTPServer" but FAST.
Yaws web server - HTTP high performance 1.1 webserver particularly well suited for dynamic-content web applications.
Vulcain - Use HTTP/2 Server Push to create fast and idiomatic client-driven REST APIs.
nghttp2 - Implementation of the Hypertext Transfer Protocol version 2 in C.
h2spec - Conformance testing tool for HTTP/2 implementation.
HTTP Made Really Easy - Practical Guide to Writing Clients and Servers.
Mini HTTP guide for developers (2020) - Glance behind the curtain: it can affect engineering decisions.
HTTP Caching (2018) - Everything you need to know about web caching.
Cassowary - Modern cross-platform HTTP load-testing tool written in Go.
TwitterServer - Defines a template from which services at Twitter are built.
miniserve - CLI tool to serve files and dirs over HTTP.
wrk - Modern HTTP benchmarking tool.
Broxy - HTTP/HTTPS intercept proxy written in Go.
Smokescreen - Simple HTTP proxy that fogs over naughty URLs.
HTTPie - CLI, cURL-like tool for humans.
http - Host These Things Please - a basic http server for hosting a folder fast and simply.
httpmole - Provides a HTTP mock server that will act as a mole among your services, telling you everything http clients send to it and responding them whatever you want it to respond.
oha - Tiny program that sends some load to a web application.
James - HTTP Proxy and Monitor that enables developers to view and intercept requests made from the browser.
FF Proxy - Proxy server which enables you to fire and forget HTTP requests.
Webhook.site - Easily test HTTP webhooks with this handy tool that displays requests instantly.
AutoCannon - Fast HTTP/1.1 benchmarking tool written in Node.js.
Servor - Dependency free file server for single page app development.
wuzz - Interactive cli tool for HTTP inspection.
DOM4 - Fully tested and covered polyfill for new DOM Level 4 entries.
templar - HTTP proxy to improve usage of HTTP APIs.
sirv - Optimized middleware & CLI application for serving static files.
Pact Go - Golang version of Pact. Pact is a contract testing framework for HTTP APIs and non-HTTP asynchronous messaging systems.
Tinyproxy - Light-weight HTTP/HTTPS proxy daemon for POSIX operating systems.
HTTP in Swift (2020) - Building a Swift HTTP framework.