CTFd

CTFd is the most widely deployed open-source platform for hosting Capture The Flag cybersecurity competitions in jeopardy-style, king-of-the-hill, and custom formats. Built with Flask, it provides challenge management, team registration, scoring, hint systems, and a real-time scoreboard with full customization through themes and plugins. CTF organizers, universities, corporate security training programs, and conference organizers use CTFd to create and manage competitive hacking events that teach and test security skills across domains including web exploitation, cryptography, forensics, and reverse engineering. The platform supports dynamic scoring, challenge dependencies, flag submission rate limiting, and integrates with containerized challenge deployment, making it the go-to solution for events ranging from small internal training exercises to large international competitions.