An adblocker is software or a browser add-on that is used to block adverts on websites. Adblockers can be installed on desktop computers, laptops, smartphones and tablets. When a user visits a website with an adblocker, the advertising content (banners, pop-ups, etc.) on the page is blocked so that the user does not see it. The adblocker analyses the HTML code of the page and filters out the advertising content before it is displayed.

Adblockers are often used to block unwanted or intrusive adverts that interfere with the browsing experience. However, ad blockers can also lead to websites generating less advertising revenue, as ad blockers prevent the delivery of adverts and can therefore harm the companies that rely on advertising.

Some websites have therefore developed strategies to circumvent adblockers, e.g. by asking visitors to deactivate the adblocker in order to gain access to the site, or by using alternative forms of advertising that are not recognised by the adblocker.