M Captcha
Add a proof-of-work CAPTCHA system to an application using the mCaptcha backend component.
About M Captcha
mCaptcha is an open-source, proof-of-work (PoW) based CAPTCHA system built as a backend component for integration into web applications. It is designed to replace traditional image-based CAPTCHAs with a seamless, automated user experience that requires no manual input beyond a single click to initiate the PoW process.
The system uses SHA256-based proof-of-work to rate limit requests, making automated abuse computationally expensive for attackers while adding only a slight delay (up to 2 seconds under attack) for legitimate users. It is privacy-focused, with no tracking cookies, IP-independent validation that works for users behind NATs, and PoW tokens that expire after 30 seconds and cannot be reused to prevent replay attacks. mCaptcha is self-hostable via Docker, and is currently in active development with no stable release as of the provided information.
Key features
- SHA256 proof-of-work based CAPTCHA validation
- Seamless one-click user experience, no manual puzzle solving
- Privacy-focused, no tracking cookies used
- IP-address independent validation for NAT users
- Replay attack resistant with 30-second token expiry
- Self-hostable via Docker Compose
Best for: Website owners seeking a privacy-focused, self-hosted CAPTCHA alternative to image-based systems that minimizes user friction.
Good for
- No manual user input required for CAPTCHA solving
- Privacy-focused with no tracking or IP dependency
- Resistant to replay attacks with short-lived tokens
- Self-hostable for full control over the system
Watch out for
- No stable release, still in active development
- Demo servers may run outdated versions behind master
- Legitimate users may experience up to 2-second delays under attack
M Captcha at a glance
- Website
- github.com/mCaptcha/mCaptcha
- Category
- Privacy & Security › Security Tools
- Type
- Open-source project
- Pricing
- Free
- Open source
- Yes · Source code
- Language
- English
- Last checked
- Oct 5, 2026 · Online when checked
- Listed
- Oct 5, 2026
Guides for Security Tools
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M Captcha FAQ
Is mCaptcha free to use?
Yes, mCaptcha is free, open-source software with no usage costs.
Does mCaptcha track user data?
No, mCaptcha does not use tracking cookies and is designed to be privacy-respecting.
How do I self-host mCaptcha?
You can self-host it by cloning the repository and running docker-compose up -d from the root directory.
What type of CAPTCHA is mCaptcha?
mCaptcha is a proof-of-work based CAPTCHA that automates validation with a single user click.
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