**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](https://github.com/feder-cr/invisible_firefox) for the full per-layer breakdown of which C++ files are patched and why.
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.
**100% Playwright-compatible** - sync and async, all methods, zero API changes. If you already use Playwright, switching is two lines:
```diff
- 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**
```python
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**
```python
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
```python
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:
```python
sf = InvisiblePlaywright()
with sf as browser:
print("seed =", sf.seed)
# ...
```
### Reproducible fingerprint
```python
with InvisiblePlaywright(seed=42) as browser:
... # same GPU, same canvas hash, same audio context, every run
```
### Proxies
```python
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.
The timezone always tracks the actual egress, so it can't disagree with the IP — a proxy in a different country paired with the host timezone is the classic `timezone_mismatch` signal. The egress IP is mapped to its IANA zone with an offline database ([`daijro/geoip-all-in-one`](https://github.com/daijro/geoip-all-in-one)), which auto-updates against its weekly rebuild and is cached locally (point `STEALTHFOX_GEOIP_MMDB` at your own `.mmdb` to skip the download). On failure: with a proxy the launch raises rather than silently using the host zone (pass an explicit `timezone=` to override); without a proxy it falls back to the host timezone so a transient lookup failure can't break the launch.
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`:
```python
from playwright.async_api import async_playwright
from invisible_playwright import ensure_binary, get_default_stealth_prefs
`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.
invisible_playwright takes a different angle than the major Firefox-hardening projects but stands on their shoulders:
- **[arkenfox/user.js](https://github.com/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](https://librewolf.net)** - 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](https://github.com/daijro/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).
MIT - see [LICENSE](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](https://github.com/feder-cr/invisible_firefox).
