6 open-source Captcha & Bot Detection vendors.

Open-source software for Captcha & Bot Detection that you can self-host, with auditable source code — regardless of the developer's headquarters.

• ALTCHASelf-hosted / open source

  Czech open-source proof-of-work captcha alternative

  Czechia

• CaptchaService (Stad München)Self-hosted / open source

  Open-source framework by the City of Munich's IT department (it-at-m) wrapping ALTCHA in a secure, multi-tenant Spring Boot microservice for government portals.

  Germany

• Gregwar Captcha BundleSelf-hosted / open source

  Widely-used, open-source web-rendering library (Symfony bundle) that generates inline image captchas on your own application server. Created by Grégoire Passault (Bordeaux, France); no controlling company.

  France

• mCaptchaSelf-hosted / open source

  Powerful open-source, standalone Proof-of-Work verification system (AGPL licence) with a full admin panel to dynamically adjust difficulty per form. Created by Aravinth Manivannan (India); no controlling company.

  India

• mosparoSelf-hosted / open source

  Open-source alternative to traditional captchas that checks form data in real time for suspicious patterns and spam traits, without tracking or external API calls. Maintained by the non-profit mosparo Association (Mellingen, Switzerland).

  Switzerland

• Swetrix CAPTCHANon-EU vendor

  Privacy-first, open-source proof-of-work verification tool (npm package @swetrix/captcha) by Swetrix Ltd, integrating seamlessly with their sovereign web-analytics platform. Registered in Edinburgh, UK; data hosted in the EU.

  United Kingdom