* [ALTCHA v3.0.11](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 JS Library v2.2.0](https://github.com/altcha-org/altcha-lib) – Lightweight, zero-dependency JavaScript library for creating and verifying ALTCHA challenges.

* [Telegram Captcha Bot v1.1.18](https://github.com/mxssl/tg-captcha-bot) – Button-based captcha for Telegram supergroups that restricts newcomers and bans users who fail to confirm within a timeout.

* [FCaptcha v1.10.1](https://github.com/WebDecoy/FCaptcha) – Detect bots, vision-based AI agents, headless browsers and automation using 40+ behavioral signals plus server-verified SHA-256 proof-of-work.

* [Cap widget@0.1.54](https://github.com/tiagozip/cap) – Lightweight, modern CAPTCHA alternative using SHA-256 proof-of-work focused on privacy and ease of integration.