Tools

The below is but a tiny fraction of all existing tools for C development; while also incomplete, more utilities can be found on similar lists we link to in the resources.
build automation
compilers
debugging
docs generators
editors/IDEs
formatters
interpreters/REPL
LSP servers
linters, analyzers
macro (pre)processors
navigation, exploration
profiling, measures
package managers
reverse engineering
transpilers
misc.
online tools
Compiler Explorer
An interactive web tool that allows you to write code and see the generated assembly output in real-time. Supports multiple compilers and provides insights into how different code constructs are translated into machine instructions.
cdecl: C gibberish ↔ English
An online version of the classic cdecl utility for "translating" C declarations to and from English.
Decompiler Explorer
An interactive online decompiler that shows equivalent C-like output of decompiled programs from many popular decompilers. It is meant to be the reverse of the Compiler Explorer.
8bitworkshop
IDE for old computers and video games. You can write code for 6502 or Z80-based hardware in C, assembly, and more.
Rextester
A simple platform for writing, sharing, compiling, and executing code directly in the web browser; with live cooperation for Patreons.
ideone.com
A platform for compiling and executing source code online, then sharing it publicly, secretly, or privately.
binvis.io
Visual analysis of binary files
Internet Archive
A lot of valuable legacy of C on the World Wide Web would be lost to time had it not been for this archive. When some hyperlink listed on C homepage inevitably fails, try checking it on IA's Wayback Machine.