Adblock killer script: what publishers actually need to know

An adblock killer script is a publisher-side tool: a small piece of JavaScript you embed in your own pages to detect ad blockers and recover the ad revenue they cost you. It is worth separating from a famous browser userscript called 'Anti-Adblock Killer', which is the opposite thing, visitors install that one to defeat the anti-adblock walls publishers put up. The two names are close enough to confuse buyers; this guide is about the publisher's adblock killer script.

An adblock killer script runs on every page view. It checks whether the visitor is running an ad blocker, uBlock Origin, AdBlock Plus, AdGuard, Brave Shields and others, and when it detects one it triggers a response, most often a polite overlay that asks the visitor to allow ads or whitelist the site so the content stays funded.

The word 'killer' is marketing, not engineering. No script running on your website can uninstall or switch off an extension in someone else's browser. What an adblock killer script actually kills is the silent revenue leak: the gap between the ads you served and the ads that were really seen. You cannot recover that gap until you can measure it, and measuring it is exactly what the script is for.

Most publishers' first move is a free, copy-paste adblock killer script. The best known is BlockAdblock, a long-running free script that drops a bait element on the page and shows a block screen when an ad blocker hides it. Around it sits a whole long tail: the IAB's open-source AdBlockDetection reference code, countless 'anti-adblock code for Blogger' and WordPress snippets, and assorted projects under the anti-adblock topic on GitHub.

The appeal is obvious. They cost nothing, install in a few minutes, and need no account. For a small blog that just wants to find out whether ad blocking is even a problem worth solving, dropping in a free adblock killer script is a reasonable first probe of the situation.

The catch is that 'free' describes the price, not the total cost. A free script is a static, public, unmaintained artifact, and that is precisely what makes it easy to neutralize. A BlockAdblock-style script that worked well two years ago detects a steadily shrinking fraction of today's blockers, and it gives you no warning as that fraction falls.

Ad blocking is an arms race. The maintainers of the major filter lists, EasyList, the uBlock Origin project, AdGuard, actively watch for popular anti-adblock scripts and publish rules that neutralize them. Because a free script like BlockAdblock is public and byte-identical on every site that uses it, it has a fixed signature: a known filename, known class names, known function names. One filter rule can disable it across every site at once.

Manifest V3 made this harder for static scripts. uBlock Origin Lite on Chrome blocks at the browser level through the declarativeNetRequest API, leaving none of the JavaScript side effects that a classic DOM-bait killer script looks for. A script that only checks whether a bait element was hidden will simply miss every visitor running a modern network-level blocker, and that share is growing.

Worst of all, a DIY script has nobody minding it. Detection that is not updated against new blocker releases and filter-list changes degrades silently: the script keeps loading, keeps reporting low numbers, and you conclude that ad blocking is a minor problem when in reality your script just stopped seeing it. It did not fail loudly with an error, it failed quietly, and quiet failure is the expensive kind.

A script that holds up in 2026 never relies on a single trick. It combines several independent signals and votes on the result, so no single filter rule can switch the whole thing off, and it is kept current as the lists change. AntiAdBlock Core is built this way and reaches roughly 99.7% detection precision across the current blocker landscape.

It must also cover both blocker paradigms: classic JavaScript filtering, which is Manifest V2 and still dominant on Firefox, and declarativeNetRequest, which is Manifest V3 and uBlock Origin Lite on Chrome. And it must avoid false positives, wrongly flagging a visitor who has no blocker, perhaps just a slow connection, damages their experience and your reputation, which means careful timeout handling and a real confidence threshold before anything is shown.

Finally, the response matters as much as the detection. Aggressively blocking the page annoys visitors and pushes them toward the very userscripts that defeat anti-adblock walls. The durable approach is a polite, on-brand overlay that explains why ads fund the content and asks the visitor to allow them, paired with analytics that show detection rate, recovery rate and estimated revenue, so you are tuning against real numbers instead of a blind counter.

Building or self-hosting your own adblock killer script gives you full control and no third-party dependency. It is a defensible choice for very large publishers with a dedicated ad-tech team that can commit to ongoing maintenance, tracking blocker releases, refreshing heuristics, re-testing across browsers every month. The script itself is cheap; the upkeep is the real cost, and it never stops.

A managed anti-adblock service moves that upkeep onto a specialist who updates detection for every customer at once. For publishers without dedicated ad-tech engineering, which is most publishers, that trade is usually worth making. Evaluate any service on three things: detection precision across the full range of blockers, the latency it adds to page load, and how it handles visitor data.

AntiAdBlock Core is built as a drop-in adblock killer script: one line of code installs the full multi-vector detection stack, a brand-friendly recovery overlay and real analytics. It is free for the first 10,000 detections each month, so you can measure your true adblock exposure before paying anything, and use that as a concrete benchmark against whatever DIY script you are running today.

Before comparing services, establish a concrete baseline. The guide on the complete guide to adblock recovery shows how to calculate the gap you are actually trying to close, and the detect uBlock Origin Lite 2026 guide explains why MV3 coverage is the single hardest part of any modern detection stack to get right.