Web Scraping & Bots · Lesson

Evading Browser Fingerprinting

Understand how sites fingerprint headless browsers and learn techniques to make automated browsers blend in with real users.

Evading Browser Fingerprinting is a free Web Scraping & Bots lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Web Scraping & Bots learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What Is Fingerprinting

Beyond IP and headers, sites profile your browser fingerprint: a combination of attributes like screen size, fonts, WebGL renderer, and JavaScript quirks that together identify automation.

Even with rotating proxies, a consistent automation fingerprint gets you blocked.

The navigator.webdriver Flag

The most obvious tell: automated browsers set navigator.webdriver to true. Scripts on the page can read this instantly.

// site-side detection
if (navigator.webdriver) {
  blockBot();
}

Headless Tells

Default headless Chrome leaks signals: a missing window.chrome object, no plugins, an unusual user-agent containing 'HeadlessChrome', and permission queries that behave oddly.

Patching webdriver

You can override the flag before the page's scripts run. Stealth libraries automate dozens of such patches, but the core idea is overriding the property.

driver.execute_cdp_cmd('Page.addScriptToEvaluateOnNewDocument', {
  'source': 'Object.defineProperty(navigator, "webdriver", {get: () => undefined})'
})

Realistic User Agents

Match your user-agent string to a real, current browser version, and keep it consistent with the platform and other headers you send. Mismatches are a red flag.

options.add_argument('user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) '
                     'AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0 Safari/537.36')

Window and Viewport Size

Headless browsers often default to tiny or unusual window sizes. Set a common resolution so the rendered viewport looks human.

options.add_argument('window-size=1920,1080')

Canvas and WebGL Noise

Sites hash the pixel output of a hidden canvas or your WebGL renderer string to build a stable ID. Adding slight randomization to these outputs breaks the consistent fingerprint.

Human-Like Behavior

Fingerprinting includes behavior. Bots click instantly and move in straight lines. Add randomized delays, mouse movement, and scrolling to mimic a person.

import random, time

for _ in range(3):
    driver.execute_script('window.scrollBy(0, arguments[0])', random.randint(200, 600))
    time.sleep(random.uniform(0.5, 1.5))

Stealth Plugins

Tools like undetected-chromedriver or selenium-stealth bundle many evasions: patching webdriver, spoofing plugins, fixing the WebGL vendor, and normalizing permissions in one step.

import undetected_chromedriver as uc
driver = uc.Chrome()
driver.get('https://example.com')

Consistency Is Key

The biggest mistake is an inconsistent profile: a Windows user-agent with a Linux WebGL renderer and a mobile screen size screams automation. Keep every signal coherent with a single believable device.

Testing Your Fingerprint

Before a real run, point your automated browser at a fingerprint-test page that reports detected automation signals. Iterate until the report looks like an ordinary browser, then deploy.

driver.get('https://bot.sannysoft.com')
# inspect the results table for red flags

Quick Check

Test your understanding of fingerprint evasion.

Recap

You learned how browser fingerprinting works and how to blend in: patch navigator.webdriver, fix headless tells, use realistic user-agents and window sizes, add canvas/WebGL noise, simulate human behavior, and keep every signal consistent.

Frequently asked questions

Is the “Evading Browser Fingerprinting” lesson free?

Yes — the full text of “Evading Browser Fingerprinting” is free to read here on the web, and the Web Scraping & Bots course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Web Scraping & Bots course, upgrade to CoddyKit PRO.

What will I learn in “Evading Browser Fingerprinting”?

Understand how sites fingerprint headless browsers and learn techniques to make automated browsers blend in with real users. You practise Web Scraping & Bots with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Web Scraping & Bots?

No prior experience is required. Web Scraping & Bots on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Evading Browser Fingerprinting” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Web Scraping & Bots lesson?

Yes. Every Web Scraping & Bots lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

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