How does ad blocking work

To put it simply, ad blocking prevents ads from loading on any websites you visit. Any type of ad, anywhere. It might seem like magic to some, but there is more to ad blockers than that. Almost like a secret agent job, ad blocking involves filter lists, intercepting server communication, and more.

And as ads permeate every surface of our online environment and become a ubiquitous part of the internet ecosystem, more and more people turn to premium ad blockers – to get rid of intrusive, overwhelming, and sometimes even malicious ads.

In this article, we provide answers to all your burning ad blocker questions: what is an ad blocker, how it works, and how they can tell the difference between a gif of a cute kitten and a flashing scam ad for the newest iPhone. Read on to find out!

What is an ad blocker?

An ad blocker is an application that detects and disables ads on websites you visit and programs you use. A simple explanation of how an ad blocker works is that it interferes and blocks website communication with ad servers and prevents ads from loading.

An ad blocker can either be a browser plugin, an extension, or a system-wide external application. The latter is more popular with mobile devices, such as phones or tablets, while browser plugins and extensions are more popular among PC users.

Some personal online security tools such as VPNs and antiviruses include an ad-blocking feature in their security suites. For example, TotalAV has Total Adblock, which effectively blocks all ads as well as trackers and prevents access to malicious and insecure websites.

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Pros and cons of an ad blocker

Considering getting an app to block ads? Here are some pros and cons of an ad blocker:

How do ad blockers work?

To put it simply, ad blockers intercept and modify webpage content to prevent the display of advertisements.

When you visit a website, your browser sends requests to retrieve various resources to load the page, including ads. Many ad blockers and similar tools have pre-defined rules, filter lists, and/or user-defined criteria for which ads (or what kind of content) to exclude.

scheme illustrating how ad blockers work: image 1

An ad blocker will compare the requests from your browser with the filtering rules, and if any of the requests are ads, it will simply prevent them from being loaded or displayed. In place of ads, an ad blocker may display a placeholder or will leave an empty space.

scheme illustrating how ad blockers work: image 2

Many advanced ad blockers allow users to choose what ads they want or don’t want to see. You can create custom rules, whitelist websites, and otherwise adjust your ad-blocking preferences.

How does AdBlock know what is an ad?

AdBlock blocks ads based on filter lists which include information about various advertisement elements, such as basic ads, pop-ups, trackers, social media ads, cookie banners, and similar. The lists can also be language-based. So when AdBlock scans a webpage, it looks for content that matches the elements in the filter list and promptly prevents it from loading.

The most widely used filter lists are from Easylist. These filter lists were designed specifically for AdBlock, but nowadays many other ad blockers use them as well.

Types of ad blockers

Not all ad blockers are the same, and some are better at one thing than the other. Generally, ad blockers can be categorized by their blocking scope – where, how many, and what kind of ads they block – and by the blocking methods that they use. Here are several different types of ad blockers:

  • Browser-based: these ad blockers are usually browser extensions or plugins and only block ads on the specific browser that they’re installed on.
  • System-wide external blocking apps: these are ad blockers that you install on your device instead of just the browser. They are capable of blocking ads both on your browser and on your device, including other applications and software.
  • In-browser ad blockers: some web browsers come with ad-blocking features pre-installed, so you don’t need to add any other extensions. Opera, Brave, and Ecosia are just some of the browsers that have integrated ad-blocking functionality.
  • DNS-based: these ad blockers use filtering at the Domain Name System level to effectively prevent ads from loading. The process involves configuring a DNS server or utilizing a DNS service that filters out requests for known advertisement domains. These DNS servers block ads by intercepting requests from users’ browsers or devices and returning a response that indicates that the requested domain doesn’t exist or redirects the request to a different IP address.

What are ad blockers used for?

The main and most obvious purpose of an ad blocker is to prevent ad displays on websites. The result is a cleaner, less cluttered, and easier-to-navigate webpage, which in turn allows users to focus on the content they came for without any distractions.

Other purposes of an ad blocker may be enhancing user privacy and online security since some ads also track user behavior and collect personal information. Sometimes ads can be malicious – leading to accidental malware or adware downloads or malicious websites. So blocking such ads effectively lowers the risk of malware infections and protects user privacy.

Are ad blockers safe?

Yes, ad blockers are safe if you choose one from a reputable source. Some free ad blockers from untrustworthy sources might be scams – instead of an ad blocker, you could infect your device with adware or other malicious programs. Such unreliable ad blockers could also collect and sell your personal data.

The popularity of ad blockers is growing. Some sources say that currently, around 43% percent of all internet users use ad blockers. According to Statista, there are around 5.16 billion internet users overall, which means that around 2.2 billion people are ad blocker users. That’s a little less than two Chinas.

Do ad blockers block all ads?

High-quality ad blockers block all types of ads, including video ads, banners, pop-ups, pop-unders, etc. The only ads that ad blockers cannot block are sponsored ads and sponsored blog posts or videos. These types of ads are often stealthy and structured as content pieces (blog posts or videos) and do not carry ad-related metadata in them, which makes them virtually impossible to block.

How content creators deal with ad blockers

For many content creators, ads are an additional (or sometimes the main) source of revenue. The increasing use of ad blockers makes it more difficult to actually earn money from displaying ads, so some platforms, websites, and creators have devised a variety of strategies to deal with ad blockers:

  • Ad-free subscriptions: many platforms offer paid subscriptions that provide an ad-free experience for the user, such as YouTube, Spotify, Twitch, Tumblr, and others. This provides a means of still making money and meeting users’ desires of not seeing ads.
  • Sponsored or native ads: such ads are usually presented as a part of webpage content – via affiliate links or otherwise. Videos may also contain ads from sponsors. Since these ads are part of the content, ad blockers can’t detect or block them without blocking access to the whole video or blog post.
  • Acceptable Ads program: this is a program initiated by AdBlock Plus with the purpose of finding the middle ground between users wanting to block all ads and the publishers who make revenue from ads. According to this program, ads need to follow a certain standard to be less intrusive. Criteria for Acceptable Ads include muted colors and non-intrusive sizes and placements of the ads. Autoplay sound or video ads, pop-ups, and oversized and animated ads aren’t considered Acceptable.
  • Ad blocker detection: some websites go the easy but more extreme way and use ad blocker detectors. The site blocks access to any webpage content unless the ad blocker is disabled.


Ad blockers are a useful tool to have if you’re tired of ads interrupting your YouTube videos, covering webpage content, and tracking your personal information.

There are many types of ad blockers, including browser extensions and system-wide ad-blocking apps. Some online privacy and security tools such as antiviruses include ad blockers in their feature suites, for example, TotalAV has Total Adblock.

But the technology behind ad blockers is usually the same: filter lists and pre-defined rules to which any webpage content gets compared. If an ad is detected, it gets blocked.

More Ad blocker guides from Cybernews:


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