Skip to content
/
reCAPTCHA v2
Last updated

reCAPTCHA v2

reCAPTCHA v2 — commonly known as the “I’m not a robot” checkbox — is one of Google’s most widely used CAPTCHA types. It may appear as a simple interactive checkbox or trigger an image/audio challenge grid. Some sites also implement it without a visible widget see reCAPTCHA Invisible Solving Guide, relying instead on callback functions to handle verification.

You can identify reCAPTCHA v2 by:

  • A visible checkbox with the label “I’m not a robot”.
  • The presence of data-sitekey in a <div class="g-recaptcha">.
  • A script URL containing www.google.com/recaptcha/api2/anchor with a k= parameter.
  • Or, in callback-based implementations, a data-callback="functionName" attribute or a callback property in a grecaptcha.render() call.
recaptcha-v2-widget.gif

Demo: Try the official Google’s reCAPTCHA v2 demo.

Integration Workflow

  1. Locate the Site Key and Page URL

    • Extract the data-sitekey value from the HTML element, or
    • Parse the k parameter from a reCAPTCHA-related script URL (e.g., in network requests).
    • Record the full page URL where the CAPTCHA appears.

  2. Submit the task:

    • For API V1: Send a request to in.php with:
    • API V2 COMING SOON

  1. Receive a task ID and wait 15–20 seconds.

  2. Poll for the result:

  1. Apply the token based on the site’s implementation:

    • Standard (form-based) implementation (most common):
      Inject the token into the hidden reCAPTCHA response field:
      document.getElementById("g-recaptcha-response").innerHTML = "TOKEN_FROM_CAPTCHA_AI";
      Then submit the form (if not auto-submitted).
  • Callback-based implementation:
    Identify the callback function name by checking:
    • data-callback="myFunction" in the reCAPTCHA <div>, or
    • The callback property in grecaptcha.render(), or
    • The global config: ___grecaptcha_cfg.clients[0].aa.l.callback (path may vary)
      Then invoke it directly with the token:
    // Replace `myFunction` with the actual callback name
myFunction("TOKEN_FROM_CAPTCHA_AI");

This function can help you identify the callback function name, just copy-paste it in the developers console on the target web page:

 function findRecaptchaClients() {
 if (typeof (___grecaptcha_cfg) !== 'undefined') {
   return Object.entries(___grecaptcha_cfg.clients).map(([cid, client]) => {
     const data = { id: cid, version: cid >= 10000 ? 'V3' : 'V2' };
     const objects = Object.entries(client).filter(([_, value]) => value && typeof value === 'object');
     objects.forEach(([toplevelKey, toplevel]) => {
       const found = Object.entries(toplevel).find(([_, value]) => (
         value && typeof value === 'object' && 'sitekey' in value && 'size' in value
       ));
       
       if (typeof toplevel === 'object' && toplevel instanceof HTMLElement && toplevel['tagName'] === 'DIV'){
         data.pageurl = toplevel.baseURI;
       }
       
       if (found) {
         const [sublevelKey, sublevel] = found;
         data.sitekey = sublevel.sitekey;
         const callbackKey = data.version === 'V2' ? 'callback' : 'promise-callback';
         const callback = sublevel[callbackKey];
         if (!callback) {
           data.callback = null;
           data.function = null;
         } else {
           data.function = callback;
           const keys = [cid, toplevelKey, sublevelKey, callbackKey].map((key) => `['${key}']`).join('');
           data.callback = `___grecaptcha_cfg.clients${keys}`;
         }
       }
     });
     console.log(data)
     return data;
   });
 }
 console.log("Can't find any reCAPTCHA client!") 
 return [];
 }
  • The g-recaptcha-response field is often hidden or inserted dynamically—use DevTools to locate it.
  • Parameter names and payload formats differ between API V1 and V2—always refer to the correct specification.

Note: Never reuse reCAPTCHA tokens. Each token is single-use and tied to a specific session and action. -->

Previous page
Next page