Private Captcha

Private Captcha is a CAPTCHA service that protects forms and APIs with a proof-of-work task. The homepage describes the task as an invisible cryptographic one. The server is written in Go, uses PostgreSQL for its backend database and ClickHouse as a second database.

The self-hosting repository runs the stack with Docker, and the quickstart describes a bootstrap script that writes the environment file. The server listens on port 8080 by default, and the admin portal is a web interface that the operator logs into with an admin email address. Intmaker OÜ, the company behind the project, also runs the managed service.

Worth knowing

The PolyForm Noncommercial license covers the community edition for non-commercial use, and commercial use of the self-hosted software needs a license under the company’s EULA. The enterprise edition is a paid self-hosted edition, and the community edition needs a license key in its environment.