https://github.com/adamsharifc/sentinel
A Chrome extension for tracker blocking and fingerprinting protection.
https://github.com/adamsharifc/sentinel
adblocking anti-fingerprinting chrome-extension fingerprinting-mitigation firefox-extension microsoft-edge-extension tracker-blocker
Last synced: about 1 month ago
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A Chrome extension for tracker blocking and fingerprinting protection.
- Host: GitHub
- URL: https://github.com/adamsharifc/sentinel
- Owner: adamsharifc
- License: mit
- Created: 2025-03-05T02:37:12.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2025-08-27T19:25:01.000Z (10 months ago)
- Last Synced: 2025-08-28T03:13:33.540Z (10 months ago)
- Topics: adblocking, anti-fingerprinting, chrome-extension, fingerprinting-mitigation, firefox-extension, microsoft-edge-extension, tracker-blocker
- Language: JavaScript
- Homepage: https://chromewebstore.google.com/detail/sentinel/pddpnjognmcdocnckfoeobncjajigpjf
- Size: 5.5 MB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Sentinel
## Install the Extension
You can install the Sentinel Chrome extension directly from your browser's add-on store:
- [Install from the Chrome Web Store](https://chromewebstore.google.com/detail/sentinel/pddpnjognmcdocnckfoeobncjajigpjf)
- [Install from the Microsoft Edge Add-ons Store](https://microsoftedge.microsoft.com/addons/detail/sentinel/bnfadclgdokiglhmjdplmmggopkjoggo)
## DNR Rulesets mapping
| Blocklist | DNR Ruleset | Description |
|-----------|-------------|-------------|
| [Easylist](https://easylist.to/easylist/easylist.txt) | `advert-dnr` | This ruleset blocks ads and trackers. |
| [Easyprivacy](https://easylist.to/easylist/easyprivacy.txt) | `tracker-dnr` | This ruleset blocks tracking scripts. |
| [Fanboy's Social Blocking List](https://easylist.to/easylist/fanboy-social.txt) | `social-dnr` | This ruleset blocks social media trackers. |
## Fingerprinting Protection
### Fingerprinting Protection Results Matrix
| Test Site / API | Canvas Fingerprint | Audio Fingerprint | WebGL Fingerprint |
|------------------------------------------------------|:-----------------:|:----------------:|:----------------:|
| [browserleaks.com/canvas](https://browserleaks.com/canvas) | ✅ Different | — | — |
| [webbrowsertools.com/canvas-fingerprint](https://webbrowsertools.com/canvas-fingerprint/) | ✅ Different | — | — |
| [webbrowsertools.com/audiocontext-fingerprint](https://webbrowsertools.com/audiocontext-fingerprint/) | — | ✅ Different / Unstable | — |
| [audiofingerprint.openwpm.com](https://audiofingerprint.openwpm.com/) | — | ✅ Different | — |
| [webbrowsertools.com/webgl-fingerprint](https://webbrowsertools.com/webgl-fingerprint/) | — | — | ✅ Different |
| [browserleaks.com/webgl](https://browserleaks.com/webgl) | — | — | ✅ Different |
**Legend:**
✅ Different — The fingerprint changes on each reload or is randomized
— Not tested / Not applicable
This matrix summarizes Sentinel's effectiveness at defeating fingerprinting on major test sites for each API.
### Canvas Fingerprinting
Sentinel protects against canvas fingerprinting by intercepting and modifying the results of canvas API calls that are commonly used for browser fingerprinting. When fingerprinting protection is enabled, Sentinel injects a content script into every page and all same-origin iframes. This script overrides key canvas methods (`getImageData`, `toDataURL`, and `toBlob`) in both the main window and any accessible iframes.
Whenever a website or script tries to read pixel data from a canvas (for example, to generate a unique fingerprint), Sentinel's overrides add subtle, random noise to the pixel data. This ensures that the fingerprint generated from the canvas will be different each time, making it unreliable for tracking users.
The extension also monitors for dynamically created iframes and patches their canvas prototypes as soon as they are accessible. This approach defeats advanced fingerprinting techniques that attempt to bypass protections by creating canvases inside iframes.
#### Tested Websites
https://browserleaks.com/canvas Different fingerprint each time.
https://webbrowsertools.com/canvas-fingerprint/ Different fingerprint each time.
### Audio Fingerprinting
Sentinel protects against audio fingerprinting by intercepting and modifying the results of key Web Audio API methods that are commonly used for browser fingerprinting. When fingerprinting protection is enabled, Sentinel injects a content script into every page and all same-origin iframes. This script overrides important Web Audio methods such as `AnalyserNode.getFloatFrequencyData`, `AudioBuffer.getChannelData`, and `OfflineAudioContext.startRendering`.
Whenever a website or script tries to read audio data for fingerprinting, Sentinel's overrides add subtle, random noise to the audio data. This ensures that the fingerprint generated from the audio context will be different each time, making it unreliable for tracking users.
The extension is careful to only add a very small amount of noise, so that legitimate audio playback and processing are not noticeably affected, but fingerprinting scripts cannot get a stable, unique value.
#### Tested Websites
- https://webbrowsertools.com/audiocontext-fingerprint/ — Breaks fingerprinting (shows indefinite loading or inconsistent results).
- https://audiofingerprint.openwpm.com/ — Different fingerprint each time.
### WebGL Fingerprinting
Sentinel protects against WebGL fingerprinting by intercepting and modifying the results of key WebGL API methods that are commonly used for browser fingerprinting. When fingerprinting protection is enabled, Sentinel injects a content script into every page and all same-origin iframes. This script overrides important WebGL methods such as `getParameter`, `getExtension`, and `readPixels`.
#### Tested Websites
- https://webbrowsertools.com/webgl-fingerprint/ — Different fingerprint each time.
- https://browserleaks.com/webgl — Different fingerprint each time.
## Firefox DNR Redirect Errors
While testing Sentinel in Firefox, you may see errors like:
#### Why do these errors occur?
Firefox does **not** allow Declarative Net Request (DNR) rules to redirect network requests to `data:` URLs (such as base64-encoded video or JavaScript). This is a browser security restriction. Chrome allows some `data:` URL redirects, but Firefox blocks them entirely.
#### How was this resolved?
To ensure compatibility with Firefox, I replaced all DNR rules that redirected to `data:` URLs with rules that simply **block** the request instead. This avoids the error and maintains effective blocking of unwanted resources.
**Summary:**
- These errors are Firefox-specific and caused by its restriction on `data:` URL redirects in DNR rules.
- The solution is to use `"block"` actions instead of `"redirect"` to `data:` URLs for maximum compatibility.