Generate Proof of Work CAPTCHAs as a ReCAPTCHA/hCaptcha alternative. Pure frontend SHA-256 computation, zero data upload, completely privacy-first.
Zero dependencies · Works offlineCopy the code below to integrate into your website:
PoW CAPTCHA Generator，（Proof of Work），ReCAPTCHAhCaptcha。SHA-256 hashing，、，。
1. Set parameters：（4bits，1-3）。
2. Generate challenge: Click "Generate Challenge" to create a random challenge string.
3. Start solving：「」，SHA-256 hashingnonce。
4. Copy code: Copy the generated client and server code to integrate PoW CAPTCHA into your website.
For privacy-conscious websites, use PoW CAPTCHA instead of Google ReCAPTCHA. No behavior tracking, no data collection, no third-party dependency — fully self-hosted and controllable.
Add PoW verification to public APIs, requiring clients to complete computation before each request — effectively preventing brute-force requests and DDoS attacks without affecting normal users.
Integrate PoW CAPTCHA into contact forms, comment systems, and registration pages to prevent automated scripts from submitting spam in bulk.
Proof of Work (PoW) was originally proposed by Adam Back in the Hashcash system to prevent email spam. The core idea: require the requester to perform computational work (finding a hash meeting specific conditions), making large-scale attacks economically infeasible. Bitcoin also uses a similar PoW mechanism to secure the blockchain. Unlike traditional image CAPTCHAs, PoW CAPTCHAs are completely transparent to users — computation runs automatically in the background with no user interaction required.
（ReCAPTCHA），。PoW，，。
Yes. PoW CAPTCHAs leverage the computational irreversibility of SHA-256 hashing. Clients must brute-force search for a nonce meeting the difficulty requirement. Increasing difficulty exponentially raises attacker costs while keeping computation time acceptable for normal users (typically 1-5 seconds).
。：1）challenge；2）PoWnonce；3）challenge+nonce；4）SHA-256。
。CPUPoW。4-5（1-3），。
。PoW，Web Crypto APISHA-256 hashing。、、。