9 projects are written in C, listed alphabetically. They are Apache HTTP Server, Hiawatha, nginx, PHP-FPM, Redict, Redis, SQLite, Valkey and Vinyl Cache. Split across servers and proxies and databases and caches. 38 records do not record this field, and cannot appear here either way. Counts only projects with momentum; the full list has the rest.
A
- Apache HTTP Server
Open-source web server for modern operating systems, extended by loadable modules.
H
HiawathaOpen source web server for Unix-like systems, focused on security and a small footprint, with CGI, FastCGI and reverse proxy support.
N
nginxC-based HTTP web server with reverse proxy, content cache, load balancer and mail proxy features.
P
- PHP-FPM
FastCGI process manager for PHP, built as an optional SAPI in the PHP source tree.
R
S
- SQLite
Public-domain C library that implements a self-contained SQL database engine in a single file.
V
ValkeyBSD-licensed in-memory key-value datastore for caching, message queues and primary database use, forked from Redis.
Vinyl CacheCaching HTTP reverse proxy, installed in front of any HTTP server to cache its responses, configured with the Vinyl Configuration Language (VCL).
What is the best web software written in C?
We can't tell from here. What suits an editor-heavy marketing site can be wrong for a static documentation site. The list is alphabetical and nobody paid for a place on it.

