Brave Core (CloverLabs Fork)

Custom fork of brave-core with per-context fingerprinting controls, stealth enhancements, and automation-friendly APIs for Playwright/Puppeteer integration.

Custom Features

Per-Context Fingerprinting Override APIs

Self-destructing JavaScript APIs that set overrides per browser context (per Playwright context). All functions delete themselves from window after the first call to prevent detection.

// Set a master seed that drives all farbling (canvas, audio, screen, WebGL, etc.)
window.setFingerprintingSeed(123456789);

// Override WebRTC local IP addresses
window.setWebRTCIPv4("192.168.1.42");
window.setWebRTCIPv6("fd00::42");

// Override browser timezone (IANA format)
window.setTimezone("Asia/Kolkata");

• Overrides persist across navigations within the same browser context
• Workers (dedicated, shared, service) automatically inherit all overrides
• Each Playwright browser context is isolated (separate renderer process)

WebGL Profile-Based Farbling

At BALANCED level (default), WebGL vendor/renderer are replaced with realistic Apple Silicon GPU profiles instead of random strings. A deterministic profile is selected per-context based on the farbling seed.

Consistent Cross-Context Farbling

Device memory, hardware concurrency, WebGL vendor/renderer, and all farbled values are guaranteed to match between the main window and worker scopes (dedicated workers, blob workers, OffscreenCanvas).

Stealth Docs

All custom stealth/fingerprinting documentation lives in src/brave/stealth_docs/:

stealth_docs/
├── HEADLESS.md      # Stealth module docs
├── PER_CONTEXT.md
├── SCREEN.md
├── WEBDRIVER.md
├── WEBRTC.md
└── design/          # Architecture and design documents

Stealth Modules

• HEADLESS.md - Headless detection and mitigation
• PER_CONTEXT.md - Per-context fingerprinting override APIs
• SCREEN.md - Screen and display fingerprinting
• WEBDRIVER.md - WebDriver detection and stealth
• WEBRTC.md - WebRTC IP leak protection

Design Documents

• MASTER_SEED_OVERRIDE.md - Master seed architecture and per-context token derivation
• WEBGL_FARBLING_PROFILES.md - WebGL profile-based farbling design (10 Apple Silicon GPU profiles)
• WEBRTC_PER_CONTEXT_COMPLETE.md - WebRTC IP override implementation
• FARBLING_COMBINATIONS.md - All farbling key combinations and PRNG behavior
• IMPLEMENTATION_SUMMARY.md - Full implementation summary across all modified files
• STEALTH.md - Stealth and anti-detection considerations
• SPEECH_DESIGN.md - Speech synthesis farbling design
• TESTING_PER_CONTEXT_API.md - Testing guide for per-context APIs

How Brave Patching and Overriding Works

Brave doesn't fork Chromium directly. Instead, brave-core sits alongside the Chromium source and uses two mechanisms to modify behavior:

1. chromium_src Overrides

Files placed in src/brave/chromium_src/ mirror the Chromium source tree structure. At build time, Brave's build system makes these files take precedence over the original Chromium files. This works through #include redirection:

src/brave/chromium_src/third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc

This file gets compiled instead of the original at:

src/third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc

Typically, the override file #includes the original and then adds macros or redefines behavior around it. This avoids maintaining a full fork of each file.

2. Patch Files

For changes that can't be done via chromium_src (e.g. modifying a header, adding a virtual method, or changing build files), Brave uses .patch files stored in src/brave/patches/. These are applied to the Chromium source during npm run init or npm run sync.

Patches live in:

src/brave/patches/                          # Chromium patches
src/brave/patches/third_party/              # Third-party dependency patches

3. Mojo Interfaces & New Files

New features (like our fingerprinting override APIs) add entirely new files in src/brave/ and connect to the browser via Mojo IPC interfaces. These don't override anything - they're additive.

How to Build

Prerequisites

Clone the repos:

git clone https://github.com/brave/brave-browser.git
git clone https://github.com/CloverLabsAI/brave-core.git brave-browser/src/brave
cd brave-browser/src/brave
npm install
npm run init

Note: All build commands must be run from src/brave/ since brave-core is a separate repo from brave-browser.

Build

If you made modifications to any patches:

npm run apply_patches

The default build type is Component.

# Component build (default - fastest for development)
npm run build

To do a Static build:

npm run build -- Static

To do a Debug build (Component with is_debug=true):

npm run build -- Debug

Note: The build will take a while. Depending on your processor and memory, it could take a few hours.

Build Configurations

We only build Component and Static builds since we can't make a Release build (requires official Brave build infrastructure and internal-only build flags like brave_stats_updater_url).

Build Type	Command	Description
Component	npm run build	Dependencies are separate shared libraries (.dylib/.so). Fastest incremental builds. Best for development.
Static	npm run build -- Static	Everything packed into one binary. Slower to build but starts faster and is self-contained. Good for testing/distribution.
Debug	npm run build -- Debug	Component build with is_debug=true. Full debug symbols and assertions.
Release	npm run build Release	Requires official Brave builder infra. We cannot build this.

Running a release build with npm run build Release can be very slow and use a lot of RAM, especially on Linux with the Gold LLVM plugin.

Platform-Specific Builds

Android:

npm run build -- --target_os=android --target_arch=arm

iOS:

Use the Xcode project found in ios/brave-ios/App. You can open it directly or run:

npm run ios_bootstrap -- --open_xcodeproj

Update / Sync to Latest Chromium & Brave

npm run sync -- [--force] [--init] [--create] [brave_core_ref]

It's safer to commit local changes before running this. The script will attempt to stash your local changes in brave-core.

npm run sync will (depending on flags):

• Update sub-projects (chromium, brave-core) to latest commit of a git ref (e.g. tag or branch)
• Apply patches
• Update gclient DEPS dependencies
• Run hooks (e.g. npm install on child projects)

Flag	Description
(no flags)	Updates chromium if needed and re-applies patches. If chromium version didn't change, only re-applies changed patches. Updates child dependencies only if any project needed updating. Use this to stay up to date.
--force	Updates both Chromium and brave-core to latest remote commit for the current branch and the Chromium ref in package.json. Re-applies all patches. Force updates all child dependencies. Use this when things are broken and you want a known-good state.
--init	Force update both Chromium and brave-core to versions in package.json and force update all dependent repos. Same as npm run init.
--sync_chromium (true/false)	Force or skip the chromium version update. Useful to avoid a large rebuild when not ready for a chromium update. A warning will show if the code expects a different version.
-D, --delete_unused_deps	Delete dependencies removed since last sync. Mimics gclient sync -D.

To checkout a specific brave-core ref and update everything:

npm run sync brave_core_ref

Resources

• Brave Browser Issues
• Brave Releases
• Brave Core Docs
• Brave Wiki