uBlock Origin — Efficient Wide-Spectrum Content Blocker

Introduction

uBlock Origin is a free, open-source browser extension that blocks ads, trackers, and malware domains. It was created to be a CPU- and memory-efficient alternative to other ad blockers, using declarative filter lists and a procedural cosmetic filtering engine. It gives users full control over what content loads in their browser.

What uBlock Origin Does

• Blocks network requests matching thousands of filter rules before content downloads
• Applies cosmetic filters to hide page elements that slip through network blocking
• Supports multiple community-maintained filter lists (EasyList, EasyPrivacy, Peter Lowe's, etc.)
• Provides per-site toggles and a dynamic filtering firewall for advanced users
• Includes a built-in logger to inspect every network request in real time

Architecture Overview

uBlock Origin parses filter lists into an optimized in-memory data structure using a static network filtering engine. Incoming HTTP requests are matched against these compiled rules before the browser fetches the resource. A separate cosmetic filtering engine injects CSS to hide leftover DOM elements. Dynamic filtering adds a firewall layer that lets users block entire domains or request types on a per-site basis. The extension runs entirely in the browser with no external server dependency.

Self-Hosting & Configuration

• Install from the official browser extension store for Firefox, Chrome, Edge, or Opera
• Default filter lists are enabled at install; add or remove lists under Dashboard > Filter lists
• Import custom filter rules in the My filters tab using Adblock Plus or uBlock Origin syntax
• Back up and restore settings with the Dashboard > Settings export/import feature
• Advanced users can enable dynamic filtering in Settings to build per-domain firewall rules

Key Features

• Minimal memory and CPU usage compared to other content blockers
• Procedural cosmetic filters that target elements by structure, not just class or ID
• Element picker mode for visually creating custom filters on any page
• Built-in request logger for debugging and transparency
• No monetization, acceptable-ads programs, or whitelisted advertisers

Comparison with Similar Tools

• Adblock Plus — uses an acceptable-ads program by default; uBlock Origin blocks all ads without exceptions
• Brave Browser — built-in blocking tied to one browser; uBlock Origin works across Firefox, Chrome, and Edge
• Pi-hole — network-level DNS blocking for all devices; uBlock Origin adds cosmetic filtering and per-element control in the browser
• Privacy Badger — focuses on tracker heuristics; uBlock Origin uses curated filter lists for broader coverage
• AdGuard — offers system-wide filtering with a paid tier; uBlock Origin is fully free and browser-based

FAQ

Q: Does uBlock Origin sell data or accept payments from advertisers? A: No. It has no monetization model and does not participate in any acceptable-ads program.

Q: Why is uBlock Origin different from uBlock? A: uBlock Origin is the original project maintained by Raymond Hill (gorhill). The name "uBlock" was forked by a different party; they are separate projects.

Q: Does it work with Manifest V3 on Chrome? A: uBlock Origin Lite is a MV3-compatible version with reduced capabilities. The full version remains fully supported on Firefox, which preserves the MV2 extension API.

Q: Will it break websites? A: Occasionally a filter rule may interfere with site functionality. Clicking the extension icon and disabling blocking for that site resolves it instantly.

Sources

• https://github.com/gorhill/uBlock
• https://ublockorigin.com