When users encounter an unresponsive or broken reCAPTCHA—such as an endless loading spinner or invalid site key—it disrupts both user experience and site security. This guide helps administrators and end users troubleshoot effectively.

1. Common Symptoms

• The reCAPTCHA widget fails to load or displays indefinitely.
• Image challenges appear but cannot be solved, even with correct selections.
• Errors such as “Invalid site key”, “Invalid domain for site key”, or “Missing input secret” appear during verification.

2. Check Browser Environment (End Users)

Quick checks for browser-related issues:

1. Update your browser — reCAPTCHA supports recent versions of Chrome, Firefox, Edge, Safari, and Chromium‑based browsers.
2. Enable JavaScript — essential for loading the widget.
3. Disable extensions — privacy blockers or script‑blocking add‑ons can interfere.
4. Clear cache & cookies, or use Incognito/private mode.
5. Restart network devices — resetting router or IP can resolve network‑related blocking .
6. Disable VPN/proxy — shared or flagged IPs often trigger reCAPTCHA security checks.
7. Try a different browser or device — isolate browser-specific issues.

3. Developer & Administrator Troubleshooting

If you're responsible for implementing reCAPTCHA:

1. Verify site key and secret key

   • “Invalid site key” often results from typos or expired keys — regenerate if necessary.
   • Ensure the site key is configured for the correct domain(s), including subdomains .

2. Client & server validation alignment

   • Ensure the client sends the token, and the server correctly verifies it with Google’s API .
   • Avoid refresh or duplicate tokens by disabling multiple form submissions or refreshing expired tokens .

3. Widget placement and resets

   • If reCAPTCHA is embedded in a modal or dynamically inserted DOM, call grecaptcha.reset() after rendering.

4. Ensure network and DNS stability

   • DNS or connectivity issues can block script loading. Flushing DNS or switching DNS settings may help.

4. Firefox-Specific Considerations

Some Firefox users experience persistent issues:

• Strict anti-fingerprint/privacy settings and DNS-over-HTTPS can prevent reCAPTCHA from loading.
• In such cases, disabling strict privacy controls—or testing in a clean profile—often restores functionality.

5. Best Practices

• Use separate keys for development and production; include localhost in dev domain settings.
• Monitor version updates — Google pushes hidden version changes which may affect older integrations .
• Provide fallback UI or error messages — to avoid dead-ends for affected users.
• Consider reCAPTCHA v3 or Enterprise — advanced versions offer invisible verification and adaptive risk scoring.

6. When All Else Fails

• Consult the site owner or developer support—end-user issues may stem from integration mistakes.
• Check browser logs for network or JavaScript errors.
• Evaluate alternative CAPTCHAs, such as hCaptcha, if privacy or usability concerns persist.
• Refer to Google’s troubleshooting guide for advanced error codes and case-specific fixes.

Conclusion

When reCAPTCHA fails to work properly, the root cause often lies in the browser environment, network settings, or improper integration. By methodically verifying browser compatibility, keys, domain settings, token handling, and reset logic, most issues can be resolved promptly. If problems continue, involving support teams or switching to alternate protection methods may be necessary.