Ad blockers promise something truly beautiful: an ad-free internet. More than that, they also prevent the internet from tracking us with cookies. Some even come bundled with VPNs — like Surfshark — that let you hide your IP from advertisers and other unknown eyes.
Now, ad blockers can be tested easily. You go to a website with ads, such as Yahoo News. You see the ads before enabling the ad blocker, and they disappear after. But that only tells you part of the story. Maybe ads on certain websites are blocked, but how do you know if your blocker won’t perform poorly on some other site?
Ad blockers that are working well today might not be able to block ads just as good tomorrow. The ever-evolving, multi-billion-dollar ad-tech industry is constantly trying to slip through your ad blockers, and sometimes they even try to nerf the ad blockers (like Google is doing with Manifest v3 on Chrome). Moreover, how do you know if your ad blocker is preventing hidden data collection through trackers?
If you think these questions are valid, and if you want to quickly test ad blockers to see which ones work better for you, you’ve come to the right place. We’re going to walk you through different tools and methods used to check if your ad-blocker is actually working. And just between us, we use some of these same methods to review ad blockers on our website, too.
How Can I Tell If My Ad Blocker Is On?
Alright, we’re gonna go do the tests, but before we do that, let’s fool-proof this guide, starting with the basics. Your ad blocker might be installed, but that doesn’t necessarily mean it’s actively blocking ads. We need to do a fast, three-step check to confirm the basics. A quick sanity check before moving on to the advanced diagnostic.
The 3-Point “Active Status” Test
1. Check the Icon
The absolute fastest way to confirm your ad blocker is running is to look at its icon in your browser toolbar. Find the icon of your ad blocker somewhere in the toolbar or in the extensions menu (often looks like a puzzle piece) in your browser.
If you can’t find it, you may need to enable it from the extensions page. For Chrome and other Chromium-based browsers like Edge or Brave, it’s at chrome://extensions, and for Firefox, it’s about:addons. Once enabled, the icon should appear on the toolbar or in the extensions menu.
Click on the icon to make sure that ad blocking is running and not paused.
2. The “Empty Space” Test
Visit a site known for heavy ad use — like Yahoo News. If your blocker is working, the advertising content is not only blocked from loading, but the ad blocker also removes the empty placeholder.
If you see large, blank, unpopulated blocks, that’s your blocker doing its most basic job: stopping the ad request and leaving an empty frame behind. This is a clear sign that the ad script failed to execute.
3. The “Acceptable Ads”
This is the most common reason a fully installed blocker is still letting ads through. Many popular extensions, by default, allow “non-intrusive” or “acceptable” advertising. This means you have a semi-porous shield.
You need to open your ad blocker’s settings page (usually by clicking the icon and finding the “Options” or “Preferences” button, often a gear icon).
Look for the checkbox labeled “Allow acceptable ads” or “Allow some non-intrusive advertising” and uncheck it. This closes a huge vulnerability and ensures you’re protected against all tracked, revenue-generating ads.
If you passed all three tests, congratulations! Your basic defenses are up. But the real test is knowing if your ad blocker is strong enough to withstand the most aggressive and sophisticated trackers. For that, we turn to the specialized tools.
How Do I Run an Ad Blocker Check?
Okay, so your basic defenses are up. You’ve confirmed the icon is shining brightly, and you’ve disabled the “acceptable ads”. Now we move from passive confirmation to active, high-stakes testing.
This is the phase where we stop guessing and start running diagnostics. The simple visual test on a news site only tells you if your blocker can handle the low-hanging fruit (basic banner ads). The dedicated testing sites are designed to throw everything at your defenses. Everything from pop-ups to tracking scripts to determine exactly how effective your shield really is.
Running the Comprehensive Diagnostic
The best way to run this test is to use one of the well-known, dedicated ad-blocking test sites. They function like an anti-virus scanner for your browser, running a barrage of checks against the most popular ad networks and trackers.
Step 1: Visit a Trusted Tester Site
There are a few reliable, well-tested sites for this. You need to visit the test site with your ad blocker fully enabled and active.
- AdBlock-Tester.com
- CanYouBlockIt.com
- d3ward’s Toolz
Step 2: Run the Comprehensive Test
Once you land on CanYouBlockIt.com, the site will immediately begin loading various types of ads and tracking scripts. Some sites offer multiple tiers of testing. Always go for the most aggressive option available:
- Simple Test: Checks against basic banner ads and contextual advertising (the easiest things to block).
- Extreme Test: This is the one you want. It subjects your blocker to the kind of aggressive formats that usually slip through: pop-ups, hidden push notifications, and network-level tracker domains. This test determines the true strength of your filter lists.
Step 3: Interpret Your Results
On AdBlock-Tester.com, it will return a score or a detailed list of blocked vs. unblocked elements. This is your personal transparency report, and it should focus on two main points:
- Script Loading: The most important metric. A good score means your blocker successfully prevented ad scripts (like those from Google AdSense or analytics platforms) from loading at all. If a script fails to load, the ad or tracker can’t execute.
- Block Visibility: This confirms whether the physical space the ad would have occupied has been successfully hidden. Even if a script is blocked, a low score here means you’re still left with an unsightly empty box.
Any score above 95% is excellent. It means the ad blocker is working fine.
My Score Was Low — Why Is My Ad Blocker Not Blocking Everything?
If your final score was anything less than perfect, don’t just see a failed number. See an opportunity. Your score didn’t fall because of a fundamental flaw in you, but because the ad-tech world is constantly improving its evasion tactics.
We frame the issue around three distinct weak points. Understanding these is the first step in taking back control:
1. The Filters are Outdated (Or Disabled)
An ad blocker is just an engine; the filter lists are the comprehensive map of known threats. If your lists are old or if you haven’t enabled the right specialist lists, the newest ads and trackers might slip right past.
Most blockers rely on EasyList as their foundational rulebook, which handles general advertising. However, this list alone is not enough for modern privacy protection. You need to go into your settings (the gear icon) and look for optional lists.
Now, there’s some trial and error here. You need to enable dedicated filters like EasyPrivacy to remove all forms of tracking, including web bugs and tracking scripts. Also, consider the Fanboy’s Annoyance List to eliminate extra clutter like cookie banners, social media buttons, and pop-ups.
While you should avoid activating too many lists at once (as it can break websites and slow your browser), you absolutely need to ensure the right anti-tracking filters are enabled to close those privacy gaps.
2. Chrome’s Manifest V3 has Limited Your Tool
This is the biggest, most cynical change in the ad-blocking landscape. The best ad blockers, like the original uBlock Origin (uBO), rely on the webRequest API to dynamically inspect and block network requests before they even load. It’s a proactive, powerful defense.
But Google’s new extension specification, Manifest V3 (MV3), severely restricts the rules extensions can use and how they function. This change only impacts Chrome and other Chromium-based browsers; Firefox is unaffected.
Because of MV3, the full version of uBlock Origin is no longer fully supported on Chrome. The MV3-compliant alternatives, such as uBlock Origin Lite (uBOL), cannot deliver the same comprehensive and dynamic blocking power. If you are a Chrome user and you see ads, this intentional “nerfing” of your ad blockers is often the cause.
3. The Ad-Tech Evasion Game is Non-Stop
Even with the right filters, ad networks and content publishers are engaged in a constant, low-level war with your ad blocker. They are always developing new ways to get their payload through.
Publishers sometimes deploy anti-adblock scripts designed specifically to detect if an ad blocker is present. Once detected, they try methods like ad reinsertion or displaying messages demanding you turn off your blocker.
This is why you must enable the Anti-Circumvention filter list in your settings. Moreover, ad networks frequently change the names or URLs of their scripts to bypass old rules. Keeping all your filter lists automatically updated is crucial.
How To Block Ads Better?
If your ad blocker isn’t working as intended, or you want it to perform better, and you have the time to tweak it. Here’s how we usually do it:
- Disable “Acceptable Ads”: This is the immediate, non-negotiable step. Go into your ad blocker’s settings and make sure that the “Allow acceptable ads” option is unchecked. This stops it from voluntarily allowing non-intrusive (but still tracking) ads.
- Audit Your Filter Lists: You can and should enable more filters than just the default EasyList. For example, if you use your ad blocker to prioritize privacy, look for EasyPrivacy and the Anti-Circumvention List to block trackers and detection scripts. And if you’re sick of the extra annoyances that aren’t exactly ads, you can enable lists like Fanboy’s Annoyance List to eliminate pop-ups, cookie banners, and social media widgets.
- Add Custom Rules: If a specific ad continues to slip through on a single site, you don’t have to wait for the next list update. You can add your own custom filter rules (e.g., using element-hiding selectors or blocking a specific URL) in your ad blocker’s advanced settings.
- Try a DNS-Based Ad Blocker: If you are concerned about in-app ads, mobile games, or trackers that persist outside of your browser, you need a DNS-level solution.
- In this case, use a trusted public DNS service like AdGuard DNS or NextDNS. These services block ads and malware at the domain level before they even reach your device, protecting your entire operating system.
- If your goal includes enhancing anonymity and blocking ads, choose a VPN provider known for a quality blocking feature like Surfshark’s CleanWeb or NordVPN’s Threat Protection. This is excellent for protection while traveling or on public Wi-Fi.
- And for the ultimate level of control and transparency, you can self-host your own network-wide DNS filter. Tools like Pi-hole or AdGuard Home cover every single device connected to your home network (including smart TVs, IoT devices, and gaming consoles) without requiring any client software on each one.
Why Am I Seeing Ads on YouTube with Ad Blocker On?
You’re probably seeing ads on YouTube because your ad blocker isn’t working, or it doesn’t work on YouTube to begin with.
Ads make up most of Google’s revenue. And people spend a lot of time on YouTube. So anything that threatens Google’s ad revenues from YouTube will eventually face some resistance. And both YouTube and Google have been cracking down on ad blockers.
The Cat-and-Mouse Game is Intentional
YouTube’s goal is to ensure you either tolerate the advertising or pay for Premium. They use a two-pronged strategy to defeat ad blockers:
- Server-Side Ad Insertion: Instead of sending the video content and the ad content separately (which allows your browser to easily block the ad file), YouTube is increasingly merging the ad directly into the video stream itself on their servers. Your ad blocker cannot easily tell where the actual content ends and the advertisement begins.
- Active Crackdown: YouTube’s engineers regularly update their code and ad delivery mechanisms to bypass known blockers. Tools like uBlock Origin rush to adapt, but YouTube just modifies its code again shortly after. They even use tactics like displaying warning banners, slowing down video load times, or completely disabling playback if an ad blocker is detected.
Not All Ad Blockers Work Equally on YouTube
Because of the extreme difficulty, not all extensions can keep up.
- Updated Filter Lists: Ad blockers that succeed on YouTube rely on ultra-fast, dynamic filter list updates. If your blocker’s developers aren’t on top of the latest changes, the ads will slip through.
- Browser Choice Matters: The Manifest V3 restrictions (which nerf Chrome extensions) make it harder for the most powerful ad blockers to function properly. This is why many experienced users often recommend Firefox for uBlock Origin, as the full, more effective version of the extension remains supported there.
The Mobile App Wall
If you are seeing ads while using the official YouTube application on your Android or iOS device, here is the short answer: no standard ad blocker extension can block them.
Browser extensions and DNS-based ad blockers typically only filter traffic at the browser or network layer. The official YouTube app is a different beast entirely. It usually uses specialized delivery methods that bypass typical browser-level filtering.
For an ad-free mobile experience, you essentially have two paths:
- Use a Private, Ad-Blocking Mobile Browser: Open the YouTube website in a browser like Firefox Mobile with uBlock Origin installed, or a privacy-focused browser that has strong built-in blocking.
- Use a patched version of the YouTube app (not recommended): Some modded YouTube apps remove ads, enable background play, add SponsorBlock, and many other features. However, these need to be sideloaded and can be malicious depending on which source you obtain them from.
Wrapping Up
If you’ve made it this far, you know more about ad blockers than most people. You know they’re not all set-it-and-forget-it tools, you know how to troubleshoot and improve their performance. And you know about the sleezy tactics ad tech companies use to track you and show you ads. Wanting a private experience on the internet is your right, and installing an ad blocker is an act of self-defense. The web is not a static place, and neither should your protection be.
Now, if you want to test your ad blocker, just go to our site home, adblock-tester.com. Anything above 90 is good enough. But there are ad blockers that hit 100. Check our list of the best ad blockers of 2025 to know more.