Fortress Review 2026: Open-Source Stealth Chromium for Agents

Most “anti-detection” browsers fix fingerprints in JavaScript — and detectors catch that instantly by checking if a function is native. Fortress takes the fundamentally harder, fundamentally more correct route: it patches Chromium’s C++ internals so the spoofed getters are native code.

What is Fortress?

Fortress is an open-source stealth Chromium engine that prevents scrapers and browser agents from being detected by anti-bot systems. It corrects browser fingerprints inside Chromium’s C++ (Blink, V8, BoringSSL) rather than via JS patches, presenting as a stock Chrome install to detectors like CreepJS, Sannysoft, BrowserScan, and Cloudflare Turnstile. It drops in as a CDP endpoint for existing Claude Code, Cursor, Playwright, Puppeteer, browser-use, or Crawl4AI automation.

Key features

• Engine-level fingerprint correction — 34 small single-purpose C++ patches modify canvas, WebGL, audio, fonts, navigator, and 30+ other surfaces in the engine itself.
• Native-code parity — every spoofed getter is a real C++ getter; toString() returns [native code], and behavior is realm-invariant across main frame, iframes, and workers.
• Drop-in CDP integration — raw Chrome DevTools Protocol on port 9222 with no Runtime.enable leak. One line of code change to your existing automation.
• Passes major bot-detection gauntlets — 0% headless on CreepJS, all-green on Sannysoft, “No bots detected” on BrowserScan, and clears live Cloudflare Turnstile; verified against real Akamai Bot Manager on major retail sites.
• Tunable persona system — one coherent default Windows identity (GPU, screen, timezone, language, voices, keyboard) with --uxr-* overrides.
• Fortress MCP server (beta) — 29 MCP tools so Claude Code or Cursor can call a stealth browser as a tool.
• Auditable open-source patches — all 34 diffs live in patches/, rebuild from source with one script; SHA-256 verified releases; BSD-3-Clause.
• Monthly Chromium rebase — gauntlet-gated releases re-run the full detector suite each cycle.

Who should use it?

Fortress is for web-scraping teams hitting Akamai/Cloudflare-protected sites, AI agent developers who need a stealth browser as a tool, and browser-automation engineers who want a drop-in anti-detection backend for existing Playwright/Puppeteer suites.

It is not a general-purpose daily browser, and there’s an important caveat: anti-bot evasion may violate the Terms of Service of target websites, and ~90% of blocks come from datacenter IPs rather than fingerprints — you still need residential/mobile proxies.

How it compares

JS-based stealth plugins (puppeteer-extra-stealth) self-reveal via toString() and realm re-acquisition — Fortress eliminates that entire detection class. Camoufox is the closest philosophical sibling (also engine-level) but Firefox-based, while Fortress uses Chromium (majority traffic). Commercial anti-detect browsers (Multilogin, GoLogin) charge $99–300+/mo for the same C++ approach but keep it closed-source; Fortress is free and auditable.

Pros and cons

Pros: architecturally correct solution; 34 auditable patches; zero-code-change CDP drop-in; proven against the hardest detectors; MCP server for agents; BSD-3-Clause with reproducible builds; monthly rebase.

Cons: early-stage (401 stars, 90 commits); no native macOS build (Docker only); CLI-based persona config; inherent arms race requiring continuous maintenance; proxy cost; ToS/legal gray area.

Pricing

Free and open source (BSD-3-Clause). A hosted MCP endpoint with residential egress is “coming soon” but unpriced; you bear proxy infrastructure cost.

FAQ

Does Fortress replace puppeteer-stealth? Yes, effectively — by fixing fingerprints in C++ rather than JavaScript, it removes the detection vectors that defeat JS plugins.

Can I keep my existing Playwright code? Yes. Point your automation at the CDP endpoint on port 9222; no script changes required.

Is it really open source? Yes — BSD-3-Clause, with all 34 patches readable in patches/ and SHA-256 verified releases. Browse related ai-chat tools for more agent browsers.