Ad Blocker

Adblockers are software products which serve to filter out advertising on websites. In addition to banner ads, pop-ups can be blocked, animations can be hidden, and ads identified in texts.


The first adblockers for Internet applications emerged in 1999. The “Webwasher Classic” software was the pioneer in this area. It was installed locally on your computer as proxy through which Internet content was retrieved. Any ads and pop-ups were filtered out.

This free application was later acquired by McAfee and is today called “McAfee Web Gateway” as a security solution for companies to filter URLs, as an anti-virus solution for Internet and email applications and SSL scanning. However, older versions of Webwasher can still be used free of charge. Other common adblockers include AdBlock, Adblock Plus, and Proxomitron.

How adblockers work

Adblockers cannot differentiate one ad from another as far as content is concerned. Instead, they filter based on special features that typically would be contained in ads. Possible approaches for adblockers are:

  • The size of the ad graphics, which is mostly standardized (e.g. 300 x 250 pixels = medium rectangle, 120 x 600 skyscraper)
  • The URL of the advertisement (collection in black and white lists)
  • Terms used in the advertising URL, which indicate advertising (such as adserv, ads)
  • The DOM structure of the ad
  • JavaScript (Advertising is often based on JavaScript)

Advantages and disadvantages

Users of adblockers can use websites without interfering advertising. In many cases, the advertising won’t even be transmitted, thus bandwidth can be saved. But even if this is not the case, the page speed will be reduced since advertising graphics do not have to be loaded. Some users also use adblockers to prevent the collection of their personal data.

Disadvantages arise especially for the provider of advertising. They often finance a substantial portion of their content based on advertising and are therefore dependent on their unrestricted display. Some companies suffer great damage in part. An expert has forecasted a loss of $887 million in advertising revenue for Google in 2012 because of adblockers.[1] For users, adblockers can be disadvantageous only if it prevents the use of free information and services, for example because the user could have “paid” with a click on an (unfortunately hidden) ad banner.

Criticism of adblockers

Adblockers have been repeatedly criticized in the past since their independence has been questioned. For example, Adblock Plus 2011 introduced an option for its users not to block “acceptable advertising.” However, this option was enabled as the default, and the user had to change the settings themselves to disable it.

The Adblock Plus operator decided which advertising would be considered acceptable after prior checking. This approach left a bad taste when it became known that large corporations were paying millions of dollars to be classified as acceptable advertising, such as content farms like eHow or Google AdWords. According to unconfirmed sources Google had paid 25 million US dollars for this purpose.

Relevance to online marketing

As already indicated, adblockers may mean sales losses for online marketing. Therefore, site operators often search for alternatives to avoid adblockers. The following options are available:

  • By means of special procedures, such as via internal or external JavaScript, adblockers can be detected. However, these methods are not 100 percent reliable.
  • Many site operators are encouraging their visitors to disable adblockers to secure their financial situation.
  • If an adblocker is detected, free content can be locked for these visitors, using appropriate procedures or default plugins for CMSs such as WordPress. Only when they deactivate their adblocker, do they “pay” for the content by the ads being enabled again and thus the content gets released.
  • Simple adblockers can be circumvented by making the advertising less obvious. For this purpose, words such as “ads” are avoided in filenames and paths, non-standardized dimensions are used for banner advertising, and the ad is stored on its own server instead of an ad server.