Cap: A Lightweight Open-Source CAPTCHA Alternative
CAPTCHAs are a necessary evil—they keep bots at bay but often frustrate users with blurry text or endless traffic lights. What if there was a simpler, more elegant solution? Enter Cap, an open-source alternative that replaces traditional CAPTCHAs with SHA-256 proof-of-work.
With over 3.1k GitHub stars and counting, Cap is gaining traction as a modern, privacy-friendly way to verify human users without the usual headaches.
What It Does
Cap ditches the traditional "solve this puzzle" approach for a cryptographic challenge. Instead of deciphering distorted text, users’ devices compute a SHA-256 hash that proves they’re willing to spend a small amount of computational effort—something bots typically avoid.
- Lightweight: No heavy dependencies, just clean JavaScript.
- Privacy-first: No tracking, no external services.
- Configurable difficulty: Adjust the proof-of-work threshold to balance security and usability.
Why It’s Cool
- No More Annoying Puzzles – Users don’t need to squint at distorted text or click endless image grids.
- Open-Source & Self-Hostable – No reliance on third-party services (looking at you, reCAPTCHA).
- Fast & Efficient – The proof-of-work computation is quick on modern devices but costly for bots scaling attacks.
How to Try It
Want to see it in action? Check out the live demo or dive into the code:
git clone https://github.com/tiagorangel1/cap.git
cd cap
npm install
npm run dev
The repo includes server integrations (like Express and Hono), a WASM-optimized solver, and a ready-to-use widget.
Final Thoughts
Cap isn’t a silver bullet—some bots could bypass it with enough resources—but for many use cases, it’s a refreshing alternative to traditional CAPTCHAs. If you’re tired of Google’s reCAPTCHA or want something more lightweight, Cap is worth a look.
What do you think? Would you use proof-of-work instead of CAPTCHAs? Let us know!
Follow us for more cool projects: @githubprojects