The story of advertising online in the last year has significantly also been a story about the rise of ad tech — ways of serving users more relevant ads, and ways of monitoring how users have responded to them. Unsurprisingly, this has also translated into a big rise in tracking technology: Adblock Plus, the popular German-based open source project that creates browser extensions and an Android app to block “annoying and intrusive” online ads, says that it now blocks 8,600 different trackers — cookies, scripts and tracking pixels on sites that run usually in the background when you visit a web site — in its EasyPrivacy filter list, more than double the number it blocked a year ago (4,200).

The trackers, in turn, collect data on usage (anonymised but still your data) to sell on to advertisers or other data management companies to help inform how advertising is bought and sold across the web, sometimes following you as you visit other sites.

Last year, Adblock found that less than 10% of advertisers made it on to their “whitelist” of acceptable advertisers based on “good behaviour” principles. These include fairly subjective points, like ads being “not annoying”, as well as more practical and more objective attributes like whether the ad is transparently an ad, or whether the ad distorts page content.

Adblock Plus’s CEO and co-founder Till Faida tells me that while that whitelist remains its “mainstay solution,” the anti-tracking that it does with tools like EasyPrivacy is offered as an additional tool for those looking for more protection. “We don’t think all tracking is bad – it can actually be useful if done transparently; but we do think you should have a robust block list if you want to get rid of it,” he says.

Tracking tools are hidden on websites and run mainly in the background in order to create unique profiles for users, which are often sold to advertising or targeting companies. For example, EasyPrivacy blocks 13 elements on nytimes.com. EasyPrivacy allows users who do not want to be followed around the web to block these tracking attempts.

Trackers are prevalent across many different pages online, including legit content sites: Adblock notes, for example, that EasyPrivacy has found 13 tracking elements on nytimes.com.

He notes that the list of trackers is definitely on the rise, currently rising at a rate of 3% in the first two months of the year. “Being open source is an advantage here, however, because more people can contribute to keeping our block list one step ahead of the trackers,” he says.

Faida says that Adblock is on track to hit 300 million downloads by next week, with active monthly users at between 50 million and 60 million at the moment. Last year, Adblock began to distribute its Android app on its own site, “since we got kicked out of Google Play”, Faida recalls. That complication and workaround have kept Android numbers “relatively low” compared to usage across Firefox, Chrome, Opera, IE and Safari browsers, Faida tells me.

Looks like we may have an update there soon, too: “We are making huge strides with the Android app that we think will bring us a lot more users in the coming year,” he says.

Photo: Flickr