Privacy glossary

Third-party ad


What is a third-party ad?

A third-party ad is a Web ad whose content is loaded from a different domain than the page showing the ad. The domain is the part of the URL after the “://” and before the next slash. For example, the domain of this page’s URL is “” The opposite of a third-party ad is a first-party ad, which is loaded from the same domain as the page showing the ad.

Why do third-party ads exist?

Websites show ads to earn revenue. However, most website owners don’t have the technical expertise to set up ad-serving technology, or the sales staff needed to sell ad space to individual advertisers.

Instead, website owners outsource those functions to ad networks. Ad networks are intermediaries: They buy ad space on websites, and sell it to advertisers. Websites can include a small piece of HTML in their pages, which tells browsers to load ad content from the ad network’s servers.

Are third-party ads bad?

Yes, third-party ads are bad for privacy. Ad networks track your browsing activity through their ads. This allows them to build a profile of your interests and spending habits, and show you ads that you’re more likely to click. Ad networks do this so they can charge advertisers higher prices for more “targeted” ad space.

Interestingly, third-party ads aren’t necessarily good for advertisers, either. In some cases they concentrate power in the hands of a few companies (the ad networks), which gives those companies leverage to dictate pricing. And over time, third-party ads lead to diminishing returns for advertisers.

Third-party ads can even slow down websites. They’re loaded from a different server than the rest of the site’s content, and if that server happens to be slow, it can make the entire site slow. And they create more data to load to the page, which can be problematic if you have low bandwidth or a poor cellular signal.

How can I avoid third-party ads?

The best way to avoid third-party ads is to use a browser, like Brave, with ad-blocking features built in. Brave blocks third-party ads by default.

Alternatively, you can install an ad-blocking extension in your browser. However, as with any extension, ad-blocking extensions can introduce privacy and performance risks of their own. They’re developed by third-party developers who may or may not be trustworthy. They may collect data about your browsing activity. They may even slow down your browser, and drain your battery life. In other words, they can cause some of the same problems that ads do.

Some browsers try to mitigate these risks by limiting what they allow extensions to do. However, that creates a different problem: With limited capabilities, extensions might not be able to do comprehensive, fully effective ad blocking. There’s a fundamental tradeoff between safe extensions and powerful extensions. Blocking features built into browsers—like Brave Shields—avoid this tradeoff entirely.

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