How to solve reCAPTCHA v2 callback

Are you developing a scraper or automating tests but running into reCAPTCHA? This guide will show you how to programmatically extract key captcha parameters (sitekey, version, callback) from a webpage and use them to bypass protection via API services. You'll learn how to run a ready-made script in the browser console, submit tasks for solving, and correctly inject the token back into the form.

Quick Start

1. Open the page with reCAPTCHA in your browser → F12 → Console tab
2. Paste the findRecaptchaClients() function code from GitHub Gist
3. Run findRecaptchaClients() and copy sitekey, version, pageurl from the output
4. Submit a task to a captcha-solving service via API
5. Receive the token and inject it into the #g-recaptcha-response field or pass it via the callback function

Video Guide

Prefer visual learning? Our video tutorial covers everything in this article with a live demonstration:

Watch the complete video guide:

What's inside the video:

• Real-time demo: Watch the entire workflow from start to finish on a live test page
• Console walkthrough: See exactly how to paste and run findRecaptchaClients() without mistakes
• Parameter extraction: Learn how to read the JSON output and identify which values matter
• API integration: Observe how to construct the API request using the extracted parameters
• Token injection: Visual demonstration of injecting the token and triggering the callback function
• Common pitfalls: See typical errors and how to avoid them in real-time

Video length: ~1 minute
Difficulty: Beginner-friendly — no prior experience required

💡 Pro tip: Watch the video first to get the big picture, then use this article as a reference while implementing it on your own project.

Step-by-Step Instructions

🔹 Step 1: Preparation and Opening the Console

• Load the target page in Chrome/Firefox
• Make sure the reCAPTCHA widget is fully rendered (sometimes a scroll or click is required)
• Open DevTools: F12 or Ctrl+Shift+I → Console tab

🔹 Step 2: Running the findRecaptchaClients Script

• Copy the function code from the official Gist
• Paste it into the console and press Enter
• Execute the command:
  javascript Copy

  findRecaptchaClients()

🔹 Step 3: Analyzing Results and Extracting Parameters

The script returns an array of objects. Example:

[
  {
    "id": "0",
    "version": "V2",
    "sitekey": "6LcTmlolAAAAAKcDAZQE0o-1rBJ4R2xz...",
    "callback": "___grecaptcha_cfg.clients['0']['C']['C']['callback']",
    "pageurl": "https://example.com/login"
  }
]

What to copy:

• sitekey — the unique site key
• version — V2 (checkbox) or V3 (invisible)
• pageurl — exact page URL (critical for validation)
• callback — optional, only if an explicit handler function exists

🔹 Step 4: Submitting the Task to the Service

Python example for reCAPTCHA v2:

import requests, time

API_KEY = 'your_api_key'
response = requests.post('https://api.rucaptcha.com/createTask', json={
    'clientKey': API_KEY,
    'task': {
        'type': 'RecaptchaV2TaskProxyless',
        'websiteURL': 'https://example.com/login',
        'websiteKey': '6LcTmlolAAAAAKcDAZQE0o-1rBJ4R2xz...'
    }
})
task_id = response.json()['taskId']

# Wait for solution
while True:
    res = requests.post('https://api.rucaptcha.com/getTaskResult', json={
        'clientKey': API_KEY, 'taskId': task_id
    }).json()
    if res['status'] == 'ready':
        token = res['solution']['gRecaptchaResponse']
        break
    time.sleep(5)

🔹 Step 5: Injecting the Token Back into the Page

# Inject token into hidden field
driver.execute_script(
    f"document.getElementById('g-recaptcha-response').value = '{token}';"
)
# Call callback if it exists
if callback:
    driver.execute_script(f"{callback}('{token}')")
# OR simply submit the form if no callback is present

Comparing Solutions

Errors and Debugging

Tip for dynamic captchas:
Run findRecaptchaClients() right before each request — don't cache sitekey long-term.

FAQ

Q: What if there are multiple captchas on the page?
A: The script returns an array — select the correct object by pageurl or visual position.

Q: Can I use this method for hCaptcha or Cloudflare?
A: No, this script works only with reCAPTCHA. Other protections require separate solutions.

Q: How can I verify the token is valid before submitting the form?
A: Send it for verification via the Google Site Verify API (requires the site's secret key).

Q: What if the site uses reCAPTCHA Enterprise?
A: The principle is the same, but additional behavioral signal emulation may be required.

Q: Is it safe to store the API key in code?
A: No. Use environment variables or your CI/CD secrets manager.

Summary

You've learned how to:

• Extract sitekey, version, and callback via the browser console
• Submit tasks to a captcha-solving service
• Correctly inject the token into the page to bypass protection

What to do next:

1. Test the script on your target page
2. Integrate the code example into your scraper or test suite
3. Set up error handling and logging
4. For production, add proxy rotation and request delays

Helpful Resources:

• findRecaptchaClients script on GitHub
• Video setup guide
• API Documentation
• Code examples for Python, JS, C# and more in our blog

Need help?
Contact support — the team responds quickly and can help with integration.

Final tip: Always verify parameter freshness on each run — sites can change their captcha implementation without notice.