Explainer
What Is an Ad Blocker?
An ad blocker is a browser extension that cancels requests to ad servers before ads download to your browser. The ad never reaches your device — it's stopped at the network level before any content transfers.
How Do Ad Blockers Work?
When your browser loads a webpage, it makes network requests for every resource on the page: images, scripts, stylesheets, and third-party embeds. Many of those requests go to ad networks and analytics services.
An ad blocker compares each outgoing request URL against a filter list — a regularly-updated text file containing rules that match known ad and tracker domains. When a request matches, the ad blocker cancels it before it completes. The ad server never receives the request; the ad content never downloads.
What Do Ad Blockers Block?
- Banner and display ads on news sites, blogs, and e-commerce sites
- Video ads on YouTube (pre-roll, mid-roll, overlay)
- Pop-up windows and overlay interstitials
- Third-party trackers (Google Analytics, Facebook Pixel, etc.)
- Malware domains used in malvertising attacks
- Browser fingerprinting scripts
What Are Filter Lists?
Filter lists are plain-text files containing rules that tell an ad blocker which URLs to block. The most widely used is EasyList, which covers the majority of ad domains. Other lists target trackers (EasyPrivacy), malware (Peter Lowe's list), and region-specific ad networks.
Filter lists are maintained by volunteer communities and updated regularly — often within hours when a new ad delivery method appears.
Acceptable Ads: What to Watch For
Some ad blockers participate in the Acceptable Ads program — a scheme where advertisers pay to have their ads whitelisted and shown even when a user has an ad blocker installed. Adblock Plus created this program; AdBlock and AdGuard also participate by default.
Ad blockers that do not participate in Acceptable Ads include ProBlocker and uBlock Origin. Every ad matching their filter rules is blocked, with no paid exceptions.
Ad blockers without Acceptable Ads →
Ad Blockers and Manifest V3
In 2024, Google enforced Manifest V3 on Chrome, removing the webRequest blocking API that most powerful ad blockers relied on. uBlock Origin was removed from the Chrome Web Store as a result. Ad blockers built for Manifest V3 — including ProBlocker — continue to work on Chrome.
Firefox was not affected. uBlock Origin works fully on Firefox.
Frequently Asked Questions
Try ProBlocker
ProBlocker is a free, open-source ad blocker extension for Chrome, Firefox, Edge, Brave, and Opera that blocks YouTube ads, pop-ups, and trackers at the network level — with no Acceptable Ads, no account, and no data collection.