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Cap

Self-hosted CAPTCHA that stops bots with invisible proof-of-work instead of visual puzzles.

Install guideWebsiteSource code
1 / 3

  • Activity Dashboard

    Per-key activity stats and visitor breakdown for a site key.

  • Integration Snippets

    Drop-in widget script, server verification code, and an AI-assistant migration prompt for a site key.

  • Challenge Configuration

    Per-key tuning for proof-of-work difficulty, instrumentation, rate limiting, and request filtering.

About this app

Cap is a lightweight, self-hosted CAPTCHA backend that replaces image and checkbox puzzles with proof-of-work and instrumentation challenges the visitor's browser solves invisibly. It runs as a single Docker container with a siteverify API and a dashboard for managing site keys, and can usually replace an existing captcha with a one-line integration change. People who choose Cap consistently point to keeping verification on their own infrastructure rather than sending visitor data to a third-party service. That distinction came up repeatedly in a Hacker News discussion of the project, weighed against cloud-only services that see every visitor's traffic. Every feature, including the dashboard and siteverify API, is available self-hosted at no cost.

  • Authentication:
    API Keys
  • Access Control:
  • Data:
  • Integrations:
    REST APIreCAPTCHA-Compatible siteverify API
  • UI:
  • Other:
    Instrumentation ChallengesProof-of-Work Challenges

Last release

standalone@3.1.8 (8 days ago*)

Last activity

3 days ago*

GitHub

tiagozip/cap

7.4k stars

515 forks

LicenseCustomOrganisation typeIndividualCountry of origin🇵🇹 PortugalHeadquartersUnknownIncorporated inUnknown

Technology stack

  • JavaScript
  • Rust
  • CSS

License

Custom

Custom or non-standard license

Apache License 2.0. Permissive open-source license with no restrictions on commercial or hosted use.

View License

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