* [ALTCHA v3.3.0](https://github.com/altcha-org/altcha) – Self-hosted privacy-first security solution protecting websites and APIs from spam using a proof-of-work mechanism.

* [ALTCHA Go Library v2.4.0](https://github.com/altcha-org/altcha-lib-go) – A Go library for creating and verifying ALTCHA v2 proof-of-work challenges, including local and remote verification support.

* [Cap standalone@3.1.13](https://github.com/tiagozip/cap) – Lightweight, modern CAPTCHA alternative using SHA-256 proof-of-work focused on privacy and ease of integration.