Private Captcha

Private Captcha is a privacy-first, EU-made proof-of-work CAPTCHA service designed for self-hosting or managed deployment. It replaces third-party tracking CAPTCHAs with a client-side puzzle approach that avoids end-user tracking and personal data collection.

Key Features

• Proof-of-Work (PoW) challenges that shift computational cost to the client instead of behavioural tracking
• Adaptive difficulty scaling that adjusts challenge complexity in real time
• Lightweight, customizable widget with an invisible mode and multiple visual themes and localizations
• Privacy- and GDPR-focused design: no end-user tracking, no cookies, minimal PII processing
• Backend usage statistics and operational metrics for domains and accounts
• RESTful platform API for automating organization and domain management
• Built with a Go backend and a JavaScript widget; uses PostgreSQL for business data and ClickHouse for operational analytics
• Optimized for low resource requirements and high-throughput environments

Use Cases

• Protect web forms and API endpoints from automated bots, spam, and scraping without third-party tracking
• Replace commercial CAPTCHA providers to meet GDPR/CCPA compliance and legal requirements
• Deploy on-premises or in EU-only infrastructure for privacy-focused organizations and projects

Limitations and Considerations

• Community edition is distributed under a PolyForm Noncommercial License; commercial use requires a paid license
• Proof-of-Work places CPU cost on clients and may impact low-power devices or increase client energy usage
• Requires running backend components (PostgreSQL and ClickHouse) which adds operational overhead compared to fully managed SaaS-only solutions

Private Captcha is a focused alternative to mainstream CAPTCHA services for organizations that need privacy-preserving, self-hostable bot protection. It emphasizes configurable difficulty, minimal tracking, and integrations for protecting forms and APIs.