mCaptcha is a privacy-respecting, proof-of-work based CAPTCHA system for developers and website owners to defend against bots and spam without tracking or annoying users.

---

🚀 Overview

mCaptcha is an open-source CAPTCHA alternative that uses SHA256 proof-of-work (PoW) to rate-limit requests, making it computationally expensive for bots and attackers while being seamless for humans. It eliminates the need for image puzzles, behavioral tracking, or third-party services like reCAPTCHA or hCaptcha.

Traditional CAPTCHAs compromise user privacy, accessibility, and UX. mCaptcha solves this by being fully self-hostable, privacy-focused, and transparent.

Answer these questions:

• What problem does this project solve? Traditional CAPTCHAs track users, have poor UX and accessibility, and rely on opaque ML. mCaptcha provides robust, privacy-preserving bot protection using PoW.
• Who is it built for? Developers, website owners, and teams needing spam/DDoS defense without privacy trade-offs.
• Why did you build it? To create a libre software solution that changes how the web defends itself, funded by NLnet, prioritizing privacy, UX, and accessibility over proprietary trackers.

---

✨ Key Features

• Privacy focused (what it does and why it matters): No cookies, tracking, or profiling—protects users from surveillance capitalism in CAPTCHAs.
• Seamless UX: Users just click a button for automatic PoW; no images or manual solving needed.
• Robust and accurate: IP-independent rate-limiting works behind NATs, replay-resistant with short-lived tokens.
• Defend like castles: PoW makes DDoS and spam attacks costly for bots.
• Libre and self-hostable: AGPL-3.0 core, easy Docker setup.
• Drop-in replacement: APIs compatible with reCAPTCHA/hCaptcha for easy migration. Optional: Upcoming features via active development on GitHub.

---

🛠 Tech Stack

• Frontend: TypeScript, HTML, SCSS, Webpack, Jest
• Backend: Rust, Actix-web
• Database: PostgreSQL or MariaDB, Redis
• Auth: Custom (admin panel with users)
• Hosting: Self-hosted, Docker/Docker Compose

---

👥 Who Is This For?

This project is useful for:

• Developers who want to ___ integrate privacy-friendly anti-bot protection
• Teams looking for ___ self-hosted DDoS/spam defense
• Indie makers building ___ transparent web apps without Big Tech dependencies

---

📸 Screenshots / Demo

• Live demo: https://demo.mcaptcha.org/
• GitHub: https://github.com/mCaptcha/mCaptcha

---

🔥 Project Status

• 🟢 Actively building

Last updated: 2026-03-24

---

❓ FAQ

Is this project free?

Yes / Freemium / Paid / Open Source Fully free and open-source (AGPL-3.0), self-hostable with no costs.

---

Is the source code available?

Yes — link to repository https://github.com/mCaptcha/mCaptcha

---

Can I contribute?

See HACKING.md for dev setup. Open issues/PRs on GitHub, join Matrix room, or provide feedback.

---

📬 Contact & Links

• Website: https://mcaptcha.org/
• GitHub: https://github.com/mCaptcha/mCaptcha
• Twitter/X: https://twitter.com/m_captcha
• Email: realaravinth@batsense.net

---

Built with ❤️ and kept warm on WarmIndex.