Adblockers explained - inside the menace that stalks publishing

Today, browsing adblockers sit plumb in the middle of an increasingly tense online stand-off between software firms, online advertisers and the web publishing industry which makes it hard to imagine their innocuous beginnings in the early 2000s.

Marketed for years by a cottage industry of coders, adblockers were just another browser utility, one of many users could choose from for all sorts off tasks. Most users didn’t use them or hadn’t even heard of them. From the outside, it was never clear whether they worked or were even particularly necessary.

Five or six years ago, something changed, although not everyone noticed at the time. Publishers with under-pressure business models started allowing more intrusive ads that splashed pop-ups, consumed bandwidth and made browsing online content more time-consuming. The clutter of third-party platforms serving these ads started out-doing each other in their attempts to attract, track and even follow users in order to target them using programmatic advertising.

Bad ads

A lot of people point the finger at these advertising platforms as the root of the problem. If they hadn't pushed advertising in the faces of users, or had been less shifty about tracking technology, blockers might never have become so popular in the first place. Others think the publishers should have taken more responsibility for what ad-delivery actually meant from the user experience and privacy point of view.

In any case, it shouldn’t have been a surprise that a growing number of users rebelled by using adblockers which were capable of stopping at least some of these ads, third-party tracking cookies and perhaps the scourge of malvertising. The trend has accelerated to the present day even though the fashion for intrusive advertising has abated. Aggressive ads are now the exception than the rule but adblockers are more common and effective than ever and it’s not hard to imagine a world where almost everyone users them for mobile as well as desktop browsers.

The genie is now long gone from a bottle publishers and ad networks hadn’t realised they were opening.

Adblockers explained - adblockers in action

How does this software work? Desktop adblockers work as browser extensions, a simple and relatively lightweight way of using software that is very easy to install and uninstall. When working, a number of techniques come into play including hardcoded lists of blacklisted URLs, by blocking known elements such as Flash and autoplay and using rule-based filter lists, of which there are numerous examples. When the user visits a webpage, adblockers act as gatekeepers intercepting and applying rules to the outgoing HTTP or HTTPS requests, stopping them from reaching the ad-serving platform in question. Less commonly, the filtering is done on the return path. Some techniques are undocumented but there is no doubt that some of them are intrusive, analysing and interfering with numerous elements on webpages.

Modern browsers such as Firefox, Chrome and IE offer a basic set of these controls (e.g. over Flash and pop-ups) but are never as comprehensive as an adblocker.

Adblockers don’t just control the visible elements of websites but, perhaps more significantly, the invisible parts too. A subset of adblockers offer privacy controls (blocking third-party cookie tracking and targeted advertising) and beacons while a few replicate the anti-phishing protection that is already built into big browser platforms.

Are they effective?

Yes. Techworld tested six leading products (Chrome + Firefox versions) against a range of websites known for ad-heavy content and can report that all were extremely effective, so much so that it’s not hard to see why publishers might be worried. Two were even able to bypass sites that asked users to turn off adblockers in order to read content, which must be even more of an anxiety.

Browser versions

The only small fly in this was that not all adblockers work equally well in all versions. Some seemed more developed on Chrome than on Firefox and in one case was more effective on the former than the latter. Adblockers are usually available on all major browsers, including in addition to the two mentioned, Safari, IE and Opera. Mobile adblockers are a different category of product that is earlier in its lifecycle but Android and, more recently, IOS apps are certainly in evidence on app stores.

The Acceptable Ads controversy

From the outside it’s incredibly hard for the uninitiated to tell one adblocker from another. There are dozens to choose from and all claim to do the job well. The important thing to remember is that while none of the well-known adblocking brands charge for browser extensions, they are in still business. A growing number are involved with the controversial Acceptable Ads system, set up by market leader Adblock Plus in 2011, which charges some large advertisers to bypass adblocking. Others simply gather anonymous data to sell on while a third, smaller group uses browser tools as loss leaders to promote subscription products in other areas of security.

Acceptable Ads is not popular with websites, a growing number of which have described it as a conflict of interest. Adblockers are supposed to filter out ads but this program makes its money by taking money to turn that off for some ads. This aspect of blockers could eventually attract the interest of EU regulators. To the cynical, adblocking can look like a clever example of a middleman business that inserts itself between end users and advertisers in order to extract a toll.

It's a live enough issue that in March 2016 UK Culture Secretary John Whittingdale used a speech to describe the adblocking business as a “modern-day protection racket,” a clear warning that governments are starting to take a concerned interest in the implications of adblocking on the publishing industry.

“Quite simply, if people don’t pay in some way for content, then that content will eventually no longer exist. And that’s as true for the latest piece of journalism as it is for the new album from Muse,” The Guardian quoted him as saying.

Eyeo, makers of Adblock Plus, defends itself by pointing out that Acceptable Ads can be turned off by end users although that is perhaps a moot point from the point of view of publishers. If all users turned off the system in their adblockers there would be no need to pay to bypass it. Most will leave it turned on.


Whittingdale wants to discuss the issue with industry insiders but it’s not clear what practical action he can take. Users will not unload adblockers just because they are damaging some publishing websites, even less so because politicians want them to. The browser is a private domain.

It is also a fact that despite their name, many tools also block ad-tracking systems that many believe represent a threat to privacy. It’s hard to see how a government could legislate against tools that perform what is a perfectly legitimate and possibly necessary function.

Adblockers explained - are adblockers obsolete?

What governments could do is regulate against the emerging trend for blocking at the network level, a technology being trialled in the UK by mobile carriers. Although this type of system is only being applied to mobile devices at present it has the potential to render software adblockers obsolete. Although network adblocking has to prove itself effective, the potential is clear.

Some see network-level adblocking – which hosts the same filtering technology on servers – is an even bigger menace than browser tools because it has the capability to turn mobile firms into even more powerful gatekeepers. This sort of control could be something end users wouldn’t even be aware of. It’s not clear whether these firms plan to build a business model like Acceptable Ads around this technology but they might think twice given the controversy surrounding that system.

As ever with adblocking the key will be what is blocked, what is not, and how those decisions are made.


Copyright © 2016 IDG Communications, Inc.

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