User-Agent Management for CAPTCHA Solving Workflows

Inconsistent or outdated user-agent strings trigger bot detection and make CAPTCHAs harder. Here's how to manage them properly.

Why User-Agent Matters

Modern User-Agent Pool

import random

# Updated Chrome UAs (keep current)
CHROME_UAS = [
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36",
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36",
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36",
]

FIREFOX_UAS = [
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:126.0) Gecko/20100101 Firefox/126.0",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:126.0) Gecko/20100101 Firefox/126.0",
    "Mozilla/5.0 (X11; Linux x86_64; rv:126.0) Gecko/20100101 Firefox/126.0",
]


def get_random_ua(browser="chrome"):
    """Get a random modern user-agent."""
    if browser == "firefox":
        return random.choice(FIREFOX_UAS)
    return random.choice(CHROME_UAS)

Session-Consistent UA

Use the same UA throughout a session:

import requests


class ConsistentSession:
    """Session that maintains consistent fingerprint."""

    def __init__(self, user_agent=None):
        self.session = requests.Session()
        self.user_agent = user_agent or get_random_ua()

        self.session.headers.update({
            "User-Agent": self.user_agent,
            "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
            "Accept-Language": "en-US,en;q=0.9",
            "Accept-Encoding": "gzip, deflate, br",
            "Connection": "keep-alive",
            "Upgrade-Insecure-Requests": "1",
        })

    def get(self, url, **kwargs):
        return self.session.get(url, **kwargs)

    def post(self, url, **kwargs):
        return self.session.post(url, **kwargs)


# Same UA for all requests in this session
session = ConsistentSession()
session.get("https://example.com/page1")
session.post("https://example.com/form")

UA Matching with CaptchaAI

Send the same UA to CaptchaAI that you use for browsing:

def solve_with_matching_ua(api_key, sitekey, pageurl, user_agent):
    """Send matching user-agent to CaptchaAI."""
    resp = requests.post("https://ocr.captchaai.com/in.php", data={
        "key": api_key,
        "method": "userrecaptcha",
        "googlekey": sitekey,
        "pageurl": pageurl,
        "userAgent": user_agent,  # Match your browser's UA
        "json": 1,
    }, timeout=30)
    return resp.json()


# Use the same UA everywhere
ua = get_random_ua()
session = ConsistentSession(user_agent=ua)

# Browse with this UA
session.get("https://example.com")

# Solve CAPTCHA with same UA
solve_with_matching_ua("YOUR_API_KEY", "SITEKEY", "https://example.com", ua)

Selenium UA Management

from selenium import webdriver
from selenium.webdriver.chrome.options import Options


def create_driver_with_ua(user_agent):
    """Create Selenium driver with specific user-agent."""
    options = Options()
    options.add_argument(f"user-agent={user_agent}")
    options.add_argument("--disable-blink-features=AutomationControlled")

    driver = webdriver.Chrome(options=options)

    # Verify UA is set correctly
    actual_ua = driver.execute_script("return navigator.userAgent")
    assert user_agent in actual_ua, f"UA mismatch: {actual_ua}"

    return driver


# Use same UA for browser and API
ua = get_random_ua()
driver = create_driver_with_ua(ua)
# ... solve with captchaai using same ua ...

Complete Headers for Realistic Requests

def get_realistic_headers(user_agent=None):
    """Build headers that match a real browser."""
    ua = user_agent or get_random_ua()

    headers = {
        "User-Agent": ua,
        "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8",
        "Accept-Language": "en-US,en;q=0.9",
        "Accept-Encoding": "gzip, deflate, br",
        "Connection": "keep-alive",
        "Upgrade-Insecure-Requests": "1",
        "Sec-Fetch-Dest": "document",
        "Sec-Fetch-Mode": "navigate",
        "Sec-Fetch-Site": "none",
        "Sec-Fetch-User": "?1",
        "Cache-Control": "max-age=0",
    }

    # Add Chrome-specific headers
    if "Chrome" in ua:
        headers["sec-ch-ua"] = '"Chromium";v="125", "Google Chrome";v="125", "Not.A/Brand";v="24"'
        headers["sec-ch-ua-mobile"] = "?0"
        headers["sec-ch-ua-platform"] = '"Windows"'

    return headers

FAQ

Does user-agent affect CAPTCHA difficulty?

Yes. reCAPTCHA and Cloudflare Turnstile analyze user-agent strings. Outdated, missing, or bot-like UAs trigger harder challenges or higher block rates.

How often should I update my UA list?

Update every 1-2 months when new browser versions release. Outdated UAs stand out in detection systems.

Should I use the same UA for all requests?

Within a session, yes. Across different sessions or accounts, rotate UAs to avoid creating a trackable pattern.

Related Guides

• IP Reputation Best Practices
• Rate Limiting CAPTCHA Solving

Build smarter automation — start with CaptchaAI.