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Best Free & Open Source Alternatives to Google reCAPTCHA

Compare 1 open-source Google reCAPTCHA alternative including ALTCHA

If you're looking for the best open-source alternative to Google reCAPTCHA; ALTCHA is a strong place to start.

#1ALTCHA

ALTCHA

Self-hosted, GDPR-compliant CAPTCHA alternative that stops spam with privacy-friendly proof-of-work challenges.

ALTCHA is a self-hosted, privacy-first CAPTCHA alternative that protects websites, APIs, and online services from spam and abuse using a proof-of-work (PoW) mechanism instead of visual puzzles. Instead of asking users to click traffic lights, the browser solves a computational challenge in the background, so most real users never see a challenge at all.

Unlike Google reCAPTCHA and hCaptcha, which run as third-party services and collect behavioral signals from visitors, ALTCHA is cookie-free and collects no data, making it GDPR, HIPAA, CCPA, and LGPD compliant out of the box. It is also engineered to WCAG 2.2 AA accessibility standards and complies with the European Accessibility Act, with audio fallbacks for users who need them. The widget is distributed as a lightweight Web Component (about 34 kB gzipped, roughly 90% smaller than reCAPTCHA).

The latest version hardens the PoW mechanism against specialized hardware by supporting memory-bound Argon2 and Scrypt algorithms, which neutralize ASIC and GPU acceleration used by bot farms. Server-side verification libraries are available for TypeScript, PHP, Python, Go, Ruby, Java, Rust, Dart, Elixir, and C++, plus starter templates for React, Vue, Svelte, Solid, Lit, and Angular. Being fully self-hosted, you keep complete sovereignty over your infrastructure with no reliance on third-party API availability or usage quotas.

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Frequently Asked Questions

Are there any open source alternatives to Google reCAPTCHA?

Yes, there are 1 open source alternatives to Google reCAPTCHA. Popular options include ALTCHA. These alternatives are free to use and many offer self-hosting options.

What is the best free alternative to Google reCAPTCHA?

The best free alternative to Google reCAPTCHA depends on your specific needs. ALTCHA is a popular choice with self-hosting capabilities. All alternatives listed here are open source and free to use.

Can I self-host an alternative to Google reCAPTCHA?

Yes, 1 of the alternatives listed here can be self-hosted, giving you complete control over your data and privacy.

Why should I switch from Google reCAPTCHA to an open source alternative?

Open source alternatives to Google reCAPTCHA offer several advantages: no vendor lock-in, complete data ownership, no subscription fees, the ability to self-host for privacy and security, and active community support. You can also customize the software to fit your specific needs.

Google reCAPTCHA

Google reCAPTCHA

Google reCAPTCHA is a free CAPTCHA and bot-detection service operated by Google. It protects websites against spam and abuse using risk analysis based on user behavior, device signals, and in newer versions, invisible background scoring. Because it runs on Google infrastructure, sites embed Google scripts and users interaction data is processed by Google, which has drawn ongoing privacy criticism in the EU.

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