SharkCaptcha
The invisible, privacy-first CAPTCHA. Stop spam and volume bots with silent proof-of-work — no image puzzles, no tracking, self-hosted on the CDNShark edge.
A drop-in replacement for reCAPTCHA and Turnstile.
Why SharkCaptcha
No street signs, no traffic lights, no "I'm not a robot" grind. Most visitors pass silently in about 200 ms.
The browser solves a small cryptographic puzzle, making bulk abuse expensive while staying instant for real people.
Self-hosted on our edge — no data sold, no cross-site tracking cookies, no third-party ad network watching your users.
A familiar widget and a server-side verify endpoint — swap out reCAPTCHA or Turnstile in minutes.
Challenges are issued from the nearest CDNShark edge, so verification is low-latency worldwide.
One script tag and one div on the client, one HTTP call to verify on your server. That's it.
How It Works
Embed the widget
Drop the SharkCaptcha script and a single element into your form.
Edge issues a challenge
The nearest CDNShark edge hands the browser a proof-of-work challenge.
Browser solves silently
The visitor's browser solves it in ~200 ms and receives a signed token.
Your server verifies
Post the token to /siteverify; a bad or missing token means block the request.
Integrate in Minutes
<script src="https://cdnshark.com/js/sharkcaptcha.js" async></script>
<form method="POST" action="/submit">
<!-- your fields -->
<div class="sharkcaptcha" data-sitekey="YOUR_SITE_KEY"></div>
<button type="submit">Send</button>
</form>POST https://cdnshark.com/captcha/siteverify
secret = YOUR_SECRET_KEY
response = <token from the form>
→ { "success": true } // allow
→ { "success": false } // rejectGet your site key and secret from the customer dashboard.
SharkCaptcha raises the cost of automated abuse and stops volume, spam, and scripted bots without annoying real visitors. Like any proof-of-work challenge, it is not designed to stop a targeted, human-solved attack — for that, pair it with CDNShark rate limiting, WAF, and bot protection for defense in depth.
Ditch the puzzles. Keep the bots out.
Add SharkCaptcha to your forms and logins in minutes.
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