captcha-go

A Go module for verifying captcha responses from Cloudflare Turnstile, Google reCAPTCHA v2 (checkbox and invisible), reCAPTCHA v3 or any other custom endpoint.

Why build another library?

This has been done before, but I had a list of requirements that weren't quite met by one I found:

• Supports Cloudflare Turnstile, Google reCAPTCHA v2, reCAPTCHA v3 (and any custom endpoint),
• Actually checks Hostname/ApkPackageName and Action,
• Doesn't use a web framework except the standard library,
• Allows setting a custom http.Client for requests,
• Makes the cdata field (from Turnstile) accessible,
• Makes proper use of errors, with helpful error messages wrapping the underlying error and without writing logs itself to the default logger.

Usage

For direct access to the response from the verification server, the CaptchaVerifier type can be used, constructed with the endpoint and secret. The Verify method takes a client response and will return a VerifyResponse which you can then check yourself.

For more abstract usage, a SimpleCaptchaVerifier can be constructed. It contains expected values for things like Hostname and Action, which are checked against responses. This means that the Verify method returns a bool, indicating if the verification succeeded and matched the expected values. More details can be found in the API documentation.