ALTCHA

ALTCHA is a self‑hosted security utility that protects websites, APIs, and online services from spam and abuse using a proof‑of‑work mechanism instead of traditional visual CAPTCHAs. It replaces intrusive techniques such as cookies or fingerprinting with background computation, delivering protection while remaining privacy‑first and fully compliant with GDPR, HIPAA, CCPA, PIPEDA/CPPA, LGPD, DPDPA, and PIPL. The solution also meets accessibility requirements, exceeding WCAG 2.2 AA standards and the European Accessibility Act.

The core widget is distributed as a Web Component that can be added to any form, and server‑side verification is supported through libraries for TypeScript, Dart, PHP, Go, Python, Java, Ruby, Elixir, Rust, and C++. ALTCHA uses memory‑bound algorithms like Argon2 and Scrypt to resist hardware‑accelerated attacks, and it offers audio‑enabled fallback challenges for visually impaired users. The implementation is lightweight, cookie‑free, and designed for rapid page loads.

Developers can customize the proof‑of‑work difficulty, choose from built‑in UI themes, and integrate with popular frameworks such as React, Vue, Svelte, Solid, Lit, and Angular. The project provides a public Playground for testing configurations and maintains a fully self‑hosted architecture, giving operators complete control over their infrastructure.