Stealth Firefox that passes every bot detection test. Drop-in Playwright replacement, fingerprint patched at the C++ level, not a JavaScript shim.

Why it's powerful

This is the actively maintained Firefox-based anti-detect browser in 2026. Camoufox pioneered the source-level patched Firefox approach, but the project has been in a roughly year-long maintenance gap and its base Firefox version is now several majors behind. CloakBrowser does the same thing for Chromium and works well, but it still hits the Chromium reCAPTCHA ceiling (~0.3-0.5). invisible_playwright ships Firefox 150 with weekly releases, source-level C++ patches end-to-end, and a measured 0.90 reCAPTCHA v3 score.

Most other anti-detect browsers patch Chromium at the JavaScript level - they override navigator, WebGLRenderingContext.getParameter, canvas APIs, and so on via injected scripts. This has two fatal problems:

1. JS patches are detectable. Anti-bots enumerate native function .toString(), check descriptor configurability, compare property enumeration order, watch for prototype mutations. Every patch leaves a fingerprint of its own. CreepJS has an entire battery of "lies detectors" built around this.
2. Chromium itself is now suspect. Residential-proxy bot traffic is overwhelmingly Chromium-based, so detectors weight anything Chromium-shaped as risky by default. Chromium-based forks inherit Chrome's open-source layers (BoringSSL, Blink, V8, ANGLE) cleanly, but they still cannot fully match Chrome in practice: Chrome ships closed-source components on top (Widevine, proprietary codecs, Google Update / Safe Browsing endpoints) that flip detectable JS feature flags and network signals, and forks lag Chrome's release cadence by days to weeks, leaving telltale version-specific behaviours that detectors lock onto.

invisible_playwright patches Firefox at the C++ level. The spoofed values come back out through the normal Gecko paths - there is no JS shim, no override, no Object.defineProperty. From the page's point of view, the browser is just telling the truth. Anti-bot lie-detectors have nothing to latch onto.

invisible_playwright spoofs all the layers that matter, together, coherently: Navigator, screen, GPU/WebGL, Canvas, fonts, audio, WebRTC, timezone, DevTools detection, SOCKS5 auth, and the rest. See feder-cr/invisible_firefox for the full per-layer breakdown of which C++ files are patched and why.

Everything is driven by preferences - no hardcoded values in the binary. You change one pref, you change the spoofed value.

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How it compares

The closest peer in the source-level patching space is Camoufox (Firefox, open source): same approach as ours, but in a roughly year-long maintenance gap with its base Firefox several majors behind. CloakBrowser ships a similar pitch for Chromium, but its binary is closed source (the source-level patches are not published, you only get the compiled output), and it still hits the Chromium reCAPTCHA ceiling. The commercial anti-detect browsers (Multilogin, GoLogin, AdsPower, Dolphin, Kameleo) are paid SaaS that overlay JS-layer spoofing on a patched Chromium. Managed profiles are nice but raw detection bypass sits below both Camoufox and us.

	invisible_playwright	Camoufox	CloakBrowser	Multilogin	GoLogin
Engine	Firefox 150	Firefox (~1 year old base)	Chromium	Chromium fork	Chromium fork
Patch depth	C++ source	C++ source	C++ source (binary only)	JS overrides	JS overrides
Maintenance	Active (weekly)	Gap (~1 year)	Active	Active SaaS	Active SaaS
Open source	✅ MIT	✅ MPL	❌ Closed source	❌ Closed source	❌ Closed source
.toString() clean	✅	✅	✅	❌ Detectable shims	❌ Detectable shims
Canvas / WebGL / Audio	✅ C++	⚠️ Drift vs current FF	✅ C++	⚠️ JS override	⚠️ JS override
SOCKS5 auth	✅ Patched	❌	⚠️ Playwright proxy	⚠️ Varies	⚠️ Varies
reCAPTCHA v3 score	0.90	~0.3-0.5	~0.3-0.5	~0.3-0.6	~0.3-0.6
FP Pro - bot detected	✅ Not detected	⚠️ Sometimes	⚠️ Sometimes	❌ Detected	❌ Detected
CreepJS lies	✅ 0	⚠️ Increasing	✅ 0	❌ Multiple	❌ Multiple
Cost	Free	Free	Free	From $99/mo	From $49/mo

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Install

pip install git+https://github.com/feder-cr/invisible_playwright.git
python -m invisible_playwright fetch      # one-time ~100 MB download, SHA256-verified

Supported platforms: Windows x86_64, Linux x86_64.

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Usage

Random fingerprint per session

100% Playwright-compatible - sync and async, all methods, zero API changes. If you already use Playwright, switching is two lines:

- from playwright.sync_api import sync_playwright
- with sync_playwright() as p:
-     browser = p.firefox.launch()
+ from invisible_playwright import InvisiblePlaywright
+ with InvisiblePlaywright() as browser:

Every session gets a unique, coherent fingerprint drawn from real-world Firefox telemetry (GPU / audio / fonts / ~400 other fields) and Bezier-curve mouse motion baked into the browser itself.

Sync

from invisible_playwright import InvisiblePlaywright

with InvisiblePlaywright(proxy={"server": "socks5://...", "username": "u", "password": "p"}) as browser:
    page = browser.new_page()
    page.goto("https://example.com")
    page.click("#submit")   # mouse arcs to the button on a Bezier curve

Async

from invisible_playwright.async_api import InvisiblePlaywright

async with InvisiblePlaywright(proxy={"server": "socks5://...", "username": "u", "password": "p"}) as browser:
    page = await browser.new_page()
    await page.goto("https://example.com")
    await page.click("#submit")

The browser object is a playwright.sync_api.Browser / playwright.async_api.Browser - every Playwright method works as-is.

---

Random fingerprint per session

from invisible_playwright import InvisiblePlaywright

with InvisiblePlaywright() as browser:
    page = browser.new_page()
    page.goto("https://creepjs-api.web.app")

Every call samples a new coherent profile. Log the seed to reproduce interesting runs:

sf = InvisiblePlaywright()
with sf as browser:
    print("seed =", sf.seed)
    # ...

Reproducible fingerprint

with InvisiblePlaywright(seed=42) as browser:
    ...   # same GPU, same canvas hash, same audio context, every run

Proxies

proxy = {
    "server": "socks5://gate.example.com:1080",
    "username": "user",
    "password": "pass",
}
with InvisiblePlaywright(proxy=proxy) as browser:
    ...

Schemes supported: socks5, socks4, http, https. Auth works on all of them (SOCKS5 via patched nsProtocolProxyService.cpp, HTTP/HTTPS via Playwright). DNS is routed through the proxy by default, no local leak.

Pinning specific fingerprint fields

By default everything comes from seed. To force specific values while the rest stays seed-derived:

with InvisiblePlaywright(
    seed=42,
    pin={
        "gpu.renderer": "ANGLE (NVIDIA, NVIDIA GeForce RTX 4090 Direct3D11)",
        "gpu.vendor":   "Google Inc. (NVIDIA)",
        "screen.width":  2560,
        "screen.height": 1440,
        "hardware.concurrency": 16,
    },
) as browser:
    ...

Full list of pinnable keys, how pinning interacts with the Bayesian sampler, and common patterns are in docs/pinning.md.

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CLI

invisible_playwright fetch          # download the binary if missing
invisible_playwright path           # print the absolute path to the cached binary
invisible_playwright version        # wrapper and binary versions
invisible_playwright clear-cache    # remove all cached binaries

Public API for downstream integrations

When you're building a third-party fetcher (a Crawlee BrowserPool subclass, a changedetection.io plugin, an agno toolkit, a Skyvern backend) and need to own the browser lifecycle yourself, use the public helpers instead of InvisiblePlaywright:

from playwright.async_api import async_playwright
from invisible_playwright import ensure_binary, get_default_stealth_prefs

async with async_playwright() as p:
    browser = await p.firefox.launch(
        executable_path=str(ensure_binary()),
        firefox_user_prefs=get_default_stealth_prefs(seed=42),
    )

get_default_stealth_prefs(seed, *, pin, locale, timezone, extra_prefs, humanize, virtual_display) returns the same dict that InvisiblePlaywright(seed=..., locale=..., ...) would inject. Same deterministic seed semantics, same humanize toggle, same extra_prefs overlay. ensure_binary() downloads the patched Firefox on first call and returns its absolute path.

Important: pass headless=False to firefox.launch() and manage display hiding yourself (Xvfb on Linux, hidden desktop on Windows). Passing headless=True directly puts Firefox in true headless mode and skips the real rendering pipeline, which breaks canvas / audio / WebGL fingerprint coherence. The InvisiblePlaywright context manager does this translation automatically; the public helpers leave it to the caller.

For everyday Python usage the InvisiblePlaywright context manager is still the recommended entry point.

Related projects

invisible_playwright takes a different angle than the major Firefox-hardening projects but stands on their shoulders:

• arkenfox/user.js - the canonical Firefox configuration for privacy/security hardening via prefs. Reading arkenfox is how you understand which user.js knobs matter; invisible_playwright goes further by patching the C++ source where prefs alone are insufficient (Canvas noise, WebGL parameter overrides, font whitelisting, WebRTC IP swap, DevTools detection bypass).
• LibreWolf - a Firefox fork bundled with sensible privacy defaults. Same audience, different distribution model: LibreWolf ships a configured Firefox binary, invisible_playwright ships source patches + a wrapper for automation.
• Camoufox - the most well-known open-source anti-detect Firefox project. We share design goals on the fingerprint-spoofing side; the implementation approach differs (Camoufox patches a wider surface and ships its own fingerprint database, while invisible_playwright sticks closer to vanilla and drives spoofing from a Bayesian sampler).

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License

MIT - see LICENSE. The patched Firefox binary is distributed under the MPL-2.0 (Firefox upstream license). The C++ patches against mozilla-central that produce that binary are at feder-cr/invisible_firefox.