Simple CAPTCHA
for modern apps.

Integrate in 60 seconds

Three changes to your existing HTML form.

<form method="POST" action="/login" data-captcha>
    <input type="email" name="email">
    <input type="password" name="password">

    <!-- optional: controls where the protection status panel appears -->
    <div data-captcha-status></div>

    <button type="submit">Login</button>
</form>

<script>
    window.CAPTCHA_BASE_URL = "https://captchaapi.eu/api/v1";
    window.CAPTCHA_SITE_KEY = "your-site-key";
</script>

<script src="https://captchaapi.eu/captcha.js" defer></script>

1. 1

   Add data-captcha to your form

   The widget automatically finds all forms with this attribute and injects the PoW challenge.

2. 2

   Set CAPTCHA_SITE_KEY

   Replace "your-site-key" with the key from your project dashboard.

3. 3

   Include captcha.js

   Load the script after your config block. It runs the PoW puzzle and appends the token to your form submission.

Get your site key

A site key ties challenges to your project and enforces your plan limits.

1. 1

   Sign up or log in

   Free plan is available with no credit card required.

2. 2

   Create a project

   Go to Dashboard → Projects → New Project. Give it a name and your domain.

3. 3

   Copy your site_key

   It's displayed on the project detail page. Paste it into your page config.

How it works

Two endpoints handle the full challenge–verify flow.

What's next