The privacy-friendly CAPTCHA that stops bots and spam.
ALTCHA blocks fake sign-ups, and form spam — with no cookies, no tracking, and no data leaving your control. Fully GDPR compliant, out of the box.
Free, self-hosted, or fully managed.
Every option is privacy-first and GDPR compliant. Pick the one that fits your team — you can switch anytime.
ALTCHA Open-Source
The free, open-source CAPTCHA widget. A great starting point for small sites.
- Proof-of-work CAPTCHA, no cookies
- 50+ languages, WCAG 2.2 AA
- No sign-up required
- Upgrade to Cloud or Sentinel anytime
- MIT licensed
ALTCHA Cloud
Sentinel, fully managed and hosted in the EU. No servers, no maintenance — live in minutes.
- Advanced protection
- Frictionless & adaptive verification
- Real-time threat intelligence
- GDPR & accessibility compliance
- EU-only endpoints
ALTCHA Sentinel
For security-conscious teams that need everything on their own infrastructure.
- Full Sentinel platform, on-premise
- Complete data sovereignty
- Runs air-gapped if required
- Docker deployment in minutes
- Support included
Global compliance & universal accessibility.
Protection that respects your users and your legal team — out of the box, in 50+ languages.
Compliance
- 100% GDPR compliant
- ePrivacy / cookie-law friendly
- No personal data collected
- Zero third-party data sharing
Accessibility
- WCAG 2.2 AA conformant
- Full keyboard navigation
- Screen-reader labelled
- No visual puzzles
Localization
- 50+ languages built in
- Right-to-left support
- Automatic language detection
- Themeable, brandable UI
Friction only for bots, not humans.
Every visitor gets the same invisible proof-of-work challenge. With Cloud or Sentinel, risk signals decide who needs anything more — an interactive check only when it's actually warranted.
A silent cryptographic challenge runs in the background. Real users never see a thing — they just submit.
When traffic looks automated, a quick accessible check confirms a human.
Live in minutes, on any stack.
Drop the widget into your site, point it at your Cloud endpoint, and you're protected. Official libraries and plugins cover every major framework and platform.
Protection without trade-offs.
| ALTCHA | reCAPTCHA | |
|---|---|---|
| No cookies or tracking scripts | ✓ | ✗ |
| No data shared with third parties | ✓ | ✗ |
| No visual puzzles to solve | ✓ | ✗ |
| Self-hosting option | ✓ | ✗ |
| Open-source core, auditable code | ✓ | ✗ |
| Data residency control | ✓ | ✗ |
Common questions
What is ALTCHA and how does it work?
A CAPTCHA alternative that verifies visitors with a silent proof-of-work challenge instead of puzzles or image quizzes — no tracking, no cookies, and nothing for real users to solve. See How ALTCHA Works for a full walkthrough.
Is ALTCHA really free?
Yes — the open-source widget is free forever, with no sign-up, API keys, or usage limits. Paid Cloud and Sentinel plans add hosted analytics and adaptive threat protection for teams that need it.
Is ALTCHA GDPR compliant without a cookie banner?
Yes. ALTCHA sets no cookies, does no fingerprinting, and shares no data with third parties, so there's nothing that requires consent. See our GDPR compliance page for details.
How hard is it to switch from reCAPTCHA or another CAPTCHA?
Most teams switch in under an hour — the widget is a drop-in replacement, and your existing form-submission flow stays the same. Step-by-step guides are available for reCAPTCHA, hCaptcha, and Cloudflare Turnstile.
Ship privacy-first protection today.
Free and open source forever. Add Cloud or Sentinel when you're ready to scale.