uBlock Origin is a free, open-source content-filtering extension from Raymond Hill and contributors. It blocks matching advertisements, trackers, and other unwanted browser content through filter lists and custom rules. Firefox support covers computers and Android. Chromium builds require browsers that retain the older extension system, while Thunderbird support filters feeds rather than email.
Requests and page appearance
Network filters stop matching requests for resources, while cosmetic filters hide elements within a page. These mechanisms handle different parts of filtering: hiding a page element alone does not prevent its network connections.
The default subscriptions include advertising, tracking, malicious-address, and uBlock filter lists. Users can change that selection or add their own rules. The popup shows blocked-request counts and the domains that the current page contacts.
Choosing subscriptions
The Filter lists dashboard groups subscriptions by purpose. Users select lists, apply their changes, or import additional subscriptions by entering one list address per line. uBlock Origin also accepts hosts-format lists and discards duplicate filters.
Automatic updates fetch newer list contents as subscriptions expire. Update now refreshes outdated lists on demand. Additional lists can also disrupt website functions when their rules match content that a page needs.
Controls for the current site
The large power button disables filtering for the current website and remembers that exception for later visits. A modifier-key click limits the exception to the current page. The Trusted sites editor accepts hostnames, individual addresses, and more specific matching patterns.
Separate site switches control particular categories:
- Popup blocking closes new popups, although it can also catch legitimate new tabs.
- The scripting switch disables JavaScript for the site.
- Remote-font blocking stops first-party and third-party web-font downloads.
- Large-media blocking uses a configurable threshold and also prevents audio or video autoplay.
Users can set global defaults and override them for individual sites. Switch changes remain temporary until the user saves them with the padlock. Size-based media blocking cannot identify oversized resources when the server omits their length.
Selecting page elements
uBlock Origin offers two tools for removing individual page elements:
| Tool | Operation | Persistence |
|---|---|---|
| Element picker | Suggests a network or cosmetic filter for the element the user selects. | Saves a site-specific rule in My filters. |
| Element zapper | Removes the element after the user highlights and selects it. | Lasts until the page reloads; creates no filter. |
The picker previews a candidate filter before creation. Sliders adjust how deeply a cosmetic selector reaches into the page and how narrowly it matches. Users can also edit the proposed text. Creation requires a valid filter that matches at least one element.
My filters provides a text editor with syntax checking and completion for manual changes. The picker and zapper operate on ordinary web pages; privileged browser pages and local-file addresses fall outside their interactive scope.
Dynamic precedence
Advanced-user mode makes the domain matrix interactive. Users create global or site-specific rules for destination hostnames and resource types. A block rule overrides matching static exceptions. A noop rule cancels broader dynamic blocking while leaving filter-list decisions in place.
Local, more specific rules take precedence over broader rules. Explicit allow rules can override static blocking, and creating them through the popup requires an additional enabling action. uBlock Origin initially treats dynamic changes as temporary; the padlock commits them. My rules also exposes the ruleset for text editing.
Inspecting matches
The logger records new filtering events while its window remains open. Rows identify the resource address, request type, page context, action, and matching filter. Users can select a page, narrow the display with expressions, and inspect which subscription supplied a filter.
Selecting a request opens tools for creating a static filter or dynamic address rule. Temporary exceptions support checking a filter’s effect and disappear when the logger closes. The export dialog copies log output to the clipboard.
Moving a configuration
A text backup preserves settings, subscription selections, custom-list addresses, personal filters, dynamic rules, and trusted sites. Restore loads that configuration again.
Optional cloud storage uses the browser’s extension-sync service. Users explicitly export a dashboard pane, import its contents, or merge them with existing settings. uBlock Origin does not synchronize these settings automatically. Availability depends on the browser’s own sync support.
