Private Captcha

Private Captcha replaces the frustrating image puzzle with a proof of work challenge the visitor's browser solves on its own. It is an independent, privacy first service made in the EU, positioned as an alternative to reCAPTCHA, hCaptcha and Cloudflare Turnstile, and it processes no personal data and no behavioral tracking.

The backend is Go, with Postgres holding business data such as accounts and properties, and ClickHouse holding operational data such as difficulty scaling and statistics. The client widget is JavaScript with WASM workers where the browser allows them, and the portal interface uses Tailwind.

The project states its goals plainly, and the feature list follows from them.

• Adaptive difficulty: challenge difficulty scales rather than staying fixed, with configuration options around it.
• Light widget: the widget is customizable and has an invisible variant for forms that should show nothing.
• Efficient backend: the server is optimized for low resource requirements and low latency under load.
• Usage statistics: the backend reports usage without collecting personal information from visitors.
• Stable integrations: the project commits to a backward compatible API over time.

A development instance starts with one make target and Docker, while production self-hosting lives in a separate repository with documentation on the main docs site, and an OpenAPI spec ships in the repo. The license is PolyForm Noncommercial, which covers self-hosting the community edition for noncommercial use, with commercial licenses sold for the enterprise edition.