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Open-source CTF platforms compared: CTFd vs rCTF vs RootTheBox and more

A maintained, dated list of self-hosted CTF platforms: license, tech stack, maintenance status, formats and GitHub stars. Plus attack-defense game servers, what self-hosting really costs, an ops checklist for event day, and an honest note on when a managed platform makes more sense.

The most popular open-source CTF platform by GitHub stars is CTFd (Apache-2.0, Python/Flask, about 6.9k stars as of October 2026). RootTheBox adds game mechanics, GZCTF adds per-team dynamic containers, and rCTF v2 (OtterSec, July 2026) adds per-team instances and webhook scoring. For attack-defense, FAUST's ctf-gameserver is the established open-source option.

Key takeaways

  • Best all-rounder: CTFd, for its maturity, docs, plugin ecosystem and permissive license. Note that King of the Hill is Enterprise-only.
  • Best for gamified classroom events: RootTheBox, with botnets, an in-game bank and a password-cracking board.
  • Best for per-team containers out of the box: GZCTF (read its dual license first) or rCTF v2, whose instancer runs on Docker or Kubernetes.
  • Attack-defense: general-purpose scoreboards (CTFd, rCTF, GZCTF) don't run A/D themselves. Dedicated game servers such as FAUST ctf-gameserver exist, but you build the vulnboxes, VPN and checkers.
  • Avoid for new events: FBCTF (archived, non-commercial license), Cardinal (archived 2024) and the original redpwn/rctf (archived; use the otter-sec fork).
  • Software is free; operations are not. Budget for servers, container isolation, backups, monitoring and someone on call during the event.

Disclosure: CTF7 is a proprietary event platform, not open source, and every one of our plans is hosted on CTF7. We maintain this list because organizers ask us for it. Star counts are rounded snapshots from GitHub on October 1, 2026 and change daily. Hosted options are covered in our CTF platform comparisons, the best platforms guide and the Hack The Box alternative breakdown.

Status table

Open-source CTF platform comparison (October 2026)

License, stars and last activity checked against each GitHub repository on October 1, 2026. Swipe sideways on mobile.

ProjectLicenseStackStars (approx.)StatusFormats
CTFdApache-2.0Python / Flask6.9k Active (commits Sep 2026)Jeopardy; KotH on Enterprise only
FBCTF (Facebook)CC BY-NC 4.0 (non-commercial)Hack / HHVM6.5k Archived, read-onlyJeopardy, KotH, world-map UI
GZCTFAGPL-3.0 core + GZCTF Restricted License componentsC# / ASP.NET Core, React1.6k Active (Sep 2026)Jeopardy with dynamic per-team containers; attack-defense (AWD) explicitly not planned
RootTheBoxApache-2.0Python / Tornado1.1k Active (Sep 2026)Jeopardy plus botnets, in-game bank, story mode
kCTF (Google)Apache-2.0Go / Kubernetes0.8k Maintained (Mar 2026)Challenge hosting infrastructure, not a scoreboard
pwn.college dojoBSD-2-ClausePython500 Active (Sep 2026)Educational challenge platform, private dojos
MellivoraGPL-3.0PHP450 No commits since Dec 2023Jeopardy
rCTF (redpwn)BSD-3-ClauseNode.js / Preact280 Archived Feb 2025Jeopardy
rCTF v2 (otter-sec)Apache-2.0TypeScript / Bun, PostgreSQL, Redis, SvelteKit130 Active (v2 released Jul 2026; commits Sep 2026)Jeopardy with per-team instances (Docker or Kubernetes); KotH and A/D scores pushed by webhook from an external engine
echoCTF.REDBSD-2-ClausePHP150 Active (Sep 2026)Target-network CTF (Docker targets)
FAUST ctf-gameserverISCPython120 Active (Sep 2026)Attack-defense game server
playCTF + Beast (SDSLabs)MIT (Beast: Apache-2.0)Vue.js frontend, Go backend70 No master commits since Aug 2022; demo and docs offlineJeopardy

"Active" means commits pushed within the last few months as of October 1, 2026; it doesn't guarantee security patches or support. Always check the repository yourself before committing to a platform. Sources at the end of this page.

Beyond the big names

More open-source CTF projects: A/D engines, training hosts and newer platforms

These show up on GitHub's ctf-platform topic and in community directories such as Rawsec's inventory and awesome-ctf. Most are smaller or more specialized, so check each repository's license file and recent activity before you plan an event around one.

ProjectWhat it isStackStars (approx.)Activity (Oct 2026)
CardinalAttack-with-defense (AWD) platform for offline events: per-round automatic scoring, a check bot, flag rotation and target status on the scoreboardGo1k Archived (Apr 2024)
multi-juicer (OWASP)Runs a separate OWASP Juice Shop instance per team for trainings and CTFs, with a progress leaderboard and auto-cleanupTypeScript / Kubernetes320 Active (Sep 2026)
ret2shellChallenge platform with a separate commercial-use policy alongside the codeRust260 Active (Sep 2026)
ForcADAttack-defense CTF platformPython190 Last push Dec 2023
CdsCTFNewer jeopardy platform focused on performanceRust60 Active (Sep 2026)
MITRE ctf-scoreboardMITRE's jeopardy and attack/defend scoreboardRuby60 Active (Sep 2026)
FlagpostNew platform: real-time scoreboard, automation rules, decay scoring, team or individual mode, CTFd-compatible import/exportDocker Compose<10 Active (Sep 2026); very new
ctf01dAttack-defense game systemC++n/aListed in Rawsec's A/D directory; check the repo
OCCPTraining platform with red, blue, gray and white team scenariosRubyn/aListed in Rawsec's A/D directory; check the repo
HaaukinsVirtualized security-education platform from Aalborg Universityn/an/aListed in awesome-ctf; check the repo

"n/a" means we didn't record a figure in our October 2026 check. Inclusion is not an endorsement; several entries in public directories are no longer maintained.

Profiles

The open-source CTF platforms, one by one

CTFd

The default choice for self-hosted jeopardy CTFs. Admin panel, themes, plugins, API, import/export and ctfcli for challenges-as-code. Hosted plans from $50/month (annual) if you'd rather not run it. KotH and some advanced features are Enterprise-only.

RootTheBox

A real-time, animated scoring engine with game mechanics: in-game botnets, "SWAT" players, an in-game bank and a board of cracked passwords. CTFtime-compatible scoreboard feed and Docker deployment. Great for classrooms and gamified events.

GZCTF

Popular with Chinese and global university teams for its per-team dynamic containers, dynamic flags and live monitoring. Dual-licensed: AGPLv3 core, plus restricted components you may use as-is but not modify without permission. Its docs say it was built to help universities train CTF teams rather than to host formal competitions.

rCTF v2

Built by redpwn in 2020; the original repo was archived on February 4, 2025. OtterSec's Apache-2.0 rewrite reached v2 in July 2026: per-team instances on Docker or Kubernetes, six scoring curves, webhook scoring for external KotH and A/D engines, an admin bot for web challenges, a Discord/Telegram blood bot, CTFtime login and export, and static archive export. Self-host only, with shared team tokens instead of individual accounts.

FAUST ctf-gameserver

The gameserver behind FAUST CTF, one of the established attack-defense competitions. Handles ticks, flag submission and service checkers. Expect expert-level setup: vulnboxes, VPN and networking are on you.

kCTF

Google's Kubernetes-based infrastructure for hosting and isolating CTF challenges. It isn't a scoreboard; pair it with CTFd or rCTF when you need hardened, scalable challenge hosting.

echoCTF.RED

A CTF and cyber-range framework focused on attacking real systems: Docker targets on a network, per-player flags. Smaller community; suits trainers building ranges.

pwn.college dojo

The open-source platform behind Arizona State University's free pwn.college. Educators can create private dojos and import or add challenges for their students. A teaching platform more than an event scoreboard.

playCTF and Beast

An Indian entry from SDSLabs, the student developer group behind Backdoor CTF: a Vue.js jeopardy frontend on the Go-based Beast backend, with Git as the source of truth for challenges and Docker isolation. The last master commit was August 2022, and its demo and docs sites were offline when we checked on October 1, 2026.

Other A/D engines

Beyond FAUST: ForcAD (Python, last push December 2023), Cardinal (Go, archived April 2024), ctf01d (C++), MITRE's ctf-scoreboard (jeopardy and attack/defend) and OCCP's team-color training scenarios. All leave the vulnbox, network and checker work to you.

Newer platforms to watch

ret2shell and CdsCTF (both Rust) and Flagpost were all pushing commits in September 2026. They're promising but young, with small communities, so check documentation depth and licensing before trusting them with a large event.

FBCTF and Mellivora

FBCTF's world-map UI still appears in older listicles, but the repo is archived and its CC BY-NC license bars commercial use. Mellivora is a lightweight PHP engine with no commits since December 2023.

How to judge

Evaluation criteria for an open-source CTF platform

A 2022 academic review of five open-source platforms (Laponina and Matoshenko, INJOIT) proposed six requirements a CTF platform should meet. They still make a useful shortlist, so we've added what to check in October 2026 and how CTF7 answers each one. One update: the review found no platform that handled live attacker-versus-defender play. That no longer holds as a general statement, because dedicated attack-defense game servers exist. The accurate version is in the A/D section below.

Criterion (2022 review)What to check in open source todayCTF7
Ease of installationIs there a supported Docker Compose or Kubernetes path for production, not only a local quick start? rCTF has a one-line installer for Docker Compose; GZCTF's docs rank a Kubernetes cluster above a single Docker host. Nothing to install on any plan, because CTF7 hosts every plan
Cross-platformWhich host OS, database, cache and object storage does it need? Most active projects assume a Linux server running containers. Web platform for players and organizers; no server to provision on hosted plans
Ease of configurationCan a non-developer create challenges, hints, flags and teams from an admin UI, or does it rely on config files and CLIs? Admin panel to upload challenges, pause rounds and track submissions live; custom branding on Standard
Status monitoringReal-time scoreboard, submission logs, challenge health and resource monitoring. Many projects leave infrastructure monitoring to you. Real-time scoreboard, organizer dashboard and post-event analytics; anti-cheat monitoring with IP and browser tracking on Standard
ExtensibilityPlugin system, API, challenges-as-code (CTFd's ctfcli, rCTF's Konata), custom challenge types. API reference; bring-your-own Docker challenge images (Standard); managed container deployment (Premium); a challenge development service
Interactivity (attacker vs defender)General-purpose scoreboards don't run A/D themselves. Dedicated A/D game servers do, but you build the vulnboxes, VPN and checkers. Attack-defense and King of the Hill as managed events our team runs, quoted per event; not self-serve

Add three criteria the 2022 review didn't weigh: maintenance status (see the status table), license fit for your institution or company, and event operations such as ticketing, fee collection and certificates, which the open-source scoreboards on this page generally leave to separate tools. For scoring mechanics, see our CTF scoring guide.

Head to head

CTFd vs rCTF vs RootTheBox: which should you self-host?

These three come up in almost every "which CTF platform" thread. Note that many third-party comparisons still describe the archived redpwn version of rCTF; the column below reflects OtterSec's v2 from July 2026.

QuestionCTFdrCTF v2 (otter-sec)RootTheBox
Best forMost jeopardy CTFs; teams that want docs and pluginsCompetitive CTFtime-style events that want a fast scoreboard with per-team instancesClassrooms and gamified events
LicenseApache-2.0Apache-2.0Apache-2.0
StackPython / FlaskTypeScript / Bun, PostgreSQL, Redis, SvelteKitPython / Tornado
EcosystemLargest: themes, plugins, ctfcli, hosted optionSmaller; pluggable providers for captcha, email, uploads and scoring, plus the Konata CLI for challenges-as-codeModerate; per a 2022 review: Rocket.Chat integration, JSON scoreboard, Juice Shop export
Standout featureMaturity and admin UXPer-team Docker or Kubernetes instancer, six scoring curves, admin bot for web challenges, CTFtime login and export, static archive exportBotnets, in-game bank, story mode
KotH and A/DKotH on Enterprise only; no documented A/D modeAccepts per-team scores from an external KotH or A/D engine through a signed webhook; doesn't run the game itselfNo built-in A/D game server (a 2022 review lists jeopardy and KotH-style play)
Watch out forKotH and some features locked to EnterpriseSelf-host only; one shared login per team; member rows are email entries, not player accounts; by design no leaderboard freeze or attempt limitsUI feels dated to some players

Want the managed-vs-CTFd angle instead? Read our CTFd alternative guide. Choosing for a campus? See CTF platforms for universities.

Attack-defense

Open-source attack-defense game servers

They exist, but not inside the popular scoreboards. As of October 2026, CTFd, rCTF and GZCTF don't run attack-defense themselves. GZCTF's docs say AWD isn't planned, and rCTF v2 only accepts scores that an external engine pushes to it. Attack-defense lives in dedicated game servers:

  • FAUST ctf-gameserver (ISC, active): ticks, flag submission and service checkers.
  • ForcAD (Python, last push December 2023) and ctf01d (C++).
  • Cardinal (Go): built for offline AWD events, archived in April 2024.
  • MITRE ctf-scoreboard (Ruby, active): jeopardy plus attack/defend scoring.

Whichever you pick, the game server is the smaller part of the job. You still build and run identical vulnboxes for every team, a VPN and network that keeps teams apart, and checkers that test every service every tick so the SLA score is fair. For how the format works, see attack-defense vs jeopardy. If you'd rather not build that stack, CTF7 runs attack-defense CTFs as a managed event, quoted per event; tell us your team count and timeline on the host-my-event form.

rCTF alternative

rCTF alternatives and hosted rCTF

rCTF v2 is a strong, opinionated platform: OtterSec reports that SekaiCTF 2026 ran it as a single application container on one Hetzner CPX62 server, peaking at about 2.6 CPU cores. As of October 2026 there's no official hosted rCTF, so you run it yourself. The docs recommend at least 2 vCPU and 4 GiB of RAM for production, and you own TLS, the reverse proxy, the instancer cluster, admin-bot workers and on-call.

People usually look for an alternative for one of four reasons:

  • No one to run the infrastructure. Pick a hosted platform: CTFd's hosted plans (see below) or CTF7 Standard, hosted like every CTF7 plan, at ₹9,999 per event for up to 500 participants with your own container challenges.
  • You need individual accounts. rCTF teams share one login token; its optional member list holds email entries, not separate player accounts (per rCTF's API docs), which matters for classes, hiring rounds and certificates. CTFd supports individual or team play; CTF7 has participant and team management with configurable team sizes and certificates.
  • You want organizer controls rCTF leaves out on purpose. Its docs list features it won't add, including leaderboard freeze, attempt limits and private scoreboards. CTFd supports score freezing and attempt limits.
  • You want A/D or KotH run for you. rCTF can display scores from an external engine, but you supply the engine. See the A/D section.

If rCTF's player-first defaults suit your event and you have the ops team, it's an excellent choice. Check the current details on OtterSec's docs before you decide.

GZCTF alternative

GZCTF alternative: when its limits don't fit

GZCTF earns its stars. It offers four challenge types (static or dynamic attachments, static or dynamic containers), per-team dynamic flags with flag-sharing detection, live monitoring, and writeup collection. Its maintainers cite a THUCTF 2022 stress test in which one 16-core, 90 GB instance handled 1.34 million requests in three minutes. Its acknowledgements page lists around 30 university CTFs that used it, from Tsinghua to UC San Diego.

The documented limits are where alternatives come in (as of October 2026; check the GZCTF docs for current details):

  • License: AGPLv3 core plus a few restricted components under a separate license. Procurement teams may want legal review.
  • No attack-defense: the Q&A says AWD/AWDP support isn't planned, citing the effort involved without revenue.
  • Self-host only: the quick start is for local testing; production means Docker or Kubernetes (K3s recommended), with HTTPS and the reverse proxy left to you. Multi-instance deployment isn't recommended, and multi-container challenges aren't supported.
  • No event commerce: no ticketing, fee collection or certificates.

Need self-hosted containers with a permissive license? Look at rCTF v2 (Apache-2.0). Need someone else to run it? CTF7 hosts every plan, and Standard includes dynamic flags, anti-cheat and bring-your-own Docker challenge images; Premium adds managed container deployment and unlimited participants. CTF7 also offers registration, fee collection and certificates as platform features.

Hosted CTFd

Hosted CTFd: what the managed version costs

Yes, CTFd is available hosted. Its publishers run managed instances on a ctfd.io subdomain or your own domain. As of October 2026 (check ctfd.io/pricing for current details), plans are billed monthly or yearly, with a one-month minimum:

Hosted CTFd planPer month, billed yearlyPer month, billed monthlyNotes
Basic$50$60250k page views a month, 5 container servers, 2,000 emails
Plus$100$120750k page views a month, 10 container servers, 5,000 emails; adds programming, multiple-choice and manual-verification challenges
Professional$300$3603M page views a month, 30 container servers, 15,000 emails; adds SAML, IP restrictions, custom theme and plugin upload
Enterprise"Contact us""Contact us"No listed price (CTFd's 2025 pricing post put it at about $500 / $600 a month). KotH, per-user application targets, browser workspaces, on-call support

Two details matter for event budgets. Per CTFd's docs, an instance that goes past 1.25x its page-view limit is automatically upgraded to the next tier, and extra email is metered. CTFd raised prices in March 2025. Its docs also describe educational discounts.

For comparison, CTF7's event plans are priced in INR with no subscription: Free (₹0, jeopardy, up to 50 participants) and Standard (₹9,999 per event, up to 500 participants, with container challenges). Both are hosted on CTF7. For a full breakdown see the CTFd alternative guide and the pricing page.

Budget

What self-hosting a CTF platform actually costs

The software is free. Your costs come from three places, and the first is usually the smallest:

  1. Infrastructure. A small cloud VM can run a scoreboard for a practice CTF. Costs climb with container challenges (every team may need its own instance), bandwidth for large attachments, a managed database, backups and a CDN or DDoS protection for public events. Price it on your cloud provider's calculator for your expected peak.
  2. People-time. Installing, hardening, load testing and upgrading the platform, then staying on call for the whole event. For a 24- or 48-hour CTF, that is at least one person awake at all times who can debug Docker, DNS and TLS.
  3. Everything around the scoreboard. Registration and fee collection, ticketing, email delivery, participant support (often a Discord server), certificates and post-event reporting. Open-source scoreboards generally leave fee collection, ticketing and certificates to separate tools.

Sizing numbers the projects publish

  • rCTF: at least 2 vCPU and 4 GiB of RAM for production; SekaiCTF 2026 peaked at about 2.6 CPU cores on one server.
  • multi-juicer: about 1 GB RAM and 1 CPU of overhead, plus 300 MB and 0.2 CPU per team. For 50 teams that's roughly 16 GB of RAM and 11 CPUs, before monitoring and backups.
  • GZCTF: the THUCTF 2022 stress test used a single 16-core, 90 GB instance.

Container challenges are what move the bill. A scoreboard alone is cheap; one instance per team per challenge is not.

Self-hosted open source vs CTF7 Free vs CTF7 Standard

Cost lineSelf-hosted open sourceCTF7 FreeCTF7 Standard
Software price₹0 (check the license)₹0₹9,999 per event
ParticipantsLimited by your serversUp to 50Up to 500
Server and hostingYour VM or cluster, database, cache, storage, TLS and reverse proxy Hosted by CTF7, like every CTF7 plan: no servers to provision and nothing to install or upgrade. See the plan details for the support included. Hosted by CTF7; no servers to provision
Maintenance hoursInstall, hardening, load tests, upgrades and teardown Nothing to install or upgrade
Platform on-callSomeone awake for the whole event who can debug Docker, DNS and TLS CTF7 runs the platform; email and WhatsApp support
Docker and KubernetesYou build and isolate the container hosting (Docker, K8s or kCTF) No container labs; static flags, attachments and external links Bring-your-own Docker challenge images
Dynamic flags and anti-cheatDepends on the platform and your configuration Not included Included
Branding and challenge extrasThemes and plugins vary by project; registration and fees need separate toolsJeopardy with static flags, attachments and external links Custom branding; hints, attachments and links

Bigger or multi-day events go on Premium (custom pricing): unlimited participants, managed container deployment, custom domain with managed SSL, advanced anti-cheat analytics and dedicated technical support. For a side-by-side estimate with your own numbers, use the CTF cost calculator. For the full planning process, see how to host a CTF, and for a campus without spare servers, running a cybersecurity lab without servers.

Ops checklist

Self-hosted CTF platform checklist

Work through this before you announce the date. Each item is something organizers have learned the hard way.

Before the event

  • Pin a platform version and read its upgrade notes; don't upgrade the week of the event.
  • Put the scoreboard behind TLS and a reverse proxy, with rate limiting on login and flag submission.
  • Isolate challenge containers from the scoreboard host and from each other; never run pwn challenges on the scoreboard VM.
  • Set resource limits (CPU, memory, process count) and automatic restarts on every challenge container.
  • Automate database backups and test a restore.
  • Load test registration, login, scoreboard and flag submission at 2–3x your expected peak.
  • Configure email sending (SPF, DKIM) so registration mails don't land in spam.
  • Decide how you'll detect flag sharing: per-team flags, submission logs, IP review.
  • Publish your rules early; our CTF rules template is a starting point.

During and after

  • Monitoring and alerts on CPU, memory, disk, error rates and challenge health checks.
  • An on-call rota covering every hour of the event, with admin access and a runbook.
  • A support channel (ticket queue or Discord) with clear rules for hint requests and disputes.
  • A plan for broken challenges: pause, fix, announce, and decide on score adjustments.
  • Announcements for downtime and scoring changes, pushed from the platform.
  • Export final scores and publish a CTFtime-compatible scoreboard feed if you're listed there (see how to list your CTF on CTFtime).
  • Archive the instance (backup export) and tear down cloud resources so the bill stops.
  • Collect writeups and feedback for the next edition.
Honest advice

When to go managed instead

Self-hosting is the right call when you have DevOps volunteers, a small or internal audience, or requirements for full code control. Consider a managed platform when:

  • You expect hundreds of players and nobody wants to be on call at 3 a.m.
  • Challenges need containers and you don't want to build the hosting and isolation yourself.
  • You charge registration fees, sell passes or issue certificates.
  • It's a hiring or assessment event where anti-cheat and audit logs matter.
  • You want attack-defense, King of the Hill, SOC simulation or report-based rounds without building a game server.

How CTF7 fits

CTF7 is not open source. It's an event platform with a Free plan for one jeopardy CTF a year with up to 50 participants, Standard at ₹9,999 per event for up to 500 (with dynamic flags, anti-cheat and bring-your-own Docker challenge images), and custom Premium events with managed container deployment and unlimited participants. Raw Ops is self-serve; attack-defense and KotH are managed events our team runs, quoted per event. Registration, fee collection and certificates are platform features too.

Would you rather not run the server?

Host a jeopardy event for up to 50 players for free on CTF7, or talk to us about a Standard or Premium event with container challenges and, on Premium, our team running them.

Read how we protect accounts and event data on the security page, or contact us with questions.

CTF7 mascot holding a CTF7 flag