Mozilla / Google / WIRED

Firefox is continuing its fight against Facebook and Google's online ad tracking empire. The browser, owned by Mozilla, will now block third-party tracking cookies by default. This Enhanced Tracking Protection will be automatically turned on for all global users as part of the standard setting. The improved privacy features have been trialled on new users since June 2019, and currently cover 20 per cent of users. From today, this will increase to 100 per cent of people using the Firefox.

Also blocked by the new protections are cryptominers: a type of malware that infiltrates your computer and leeches computing power and battery to mine cryptocurrencies. This feature was previously on offer in Firefox Nightly and Beta, but will now be included in the standard mode by default. When the feature is enabled, a shield icon in the search bar indicates that the website’s cookies are being blocked. Users will be able to see all of the third party cookies that are being blocked, and adjust this if they wish to give certain companies a carte blanche.


Why is this important? While most of us generally click absentmindedly to ‘accept cookies’ for the sites we alight on, these invisible hangers-on constitute a surprisingly insidious means of tracking your behaviour across the web. Pervasive ad tracking means that someone’s entire web browsing history can be effectively recreated by third party companies – and this information can then be swapped across the web by various information resellers. Private mode and that the majority of porn sites are infested by hundreds of trackers – including from Google and Facebook.

"Currently, users are being taken advantage of and being left out of that value exchange," a spokesperson for Mozilla said. "They’re tracked across sites by entities which they never interact with."

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But cookies aren't the only method of tracking. Billed for a future Firefox update is default restriction of fingerprinting scripts, which snatch a snapshot of your computer’s configuration when you visit a website, and use it to track you across the web. For example, gleaning information such as what device you’re using or even what font you have installed can be leveraged to create a unique identity for your online behaviour to be stored against. Currently, users can insulate themselves from fingerprinting in Firefox by enabling the strict mode. However, in future the company expects this will be turned on by default too.

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Firefox has long tried to make privacy its USP – while Google has forged ahead to a 70 per cent market share of web browser usage on desktop. Firefox has a ten per cent share of browser usage. This most recent update shifts the service more firmly at odds to the likes of Google and Facebook, who rely on cookies as part of their ad serving business models. However, Firefox is far from the only cookie conscious browser in this space.

Apple has been restricting cookie monitoring since 2017 with the launch of Safari 11. The company's Intelligent Tracking Prevention (ITP) uses machine learning algorithms to identify tracking behaviour, such as persistent cookies from third party ad networks. These allow ads to follow users across the web. Safari imposes 24 hour windows on the lifespan of these tracking tools, in a move Apple said was more about protecting user privacy than blocking ads. However, these measures might not make a dent in the business models of Facebook and Google – whose stranglehold on search and social media spheres respectively means many people keep them running in the background all the time.

Google, notorious for its obsessive tracking of user data, has also indicated a desire to step up its browser's privacy features. In a blogpost published on August 22, the company said that indiscriminate blocking of cookies could prove ruinous to publisher's revenue stream, as well as harming the consumer, by encouraging more opaque techniques such as fingerprinting to flourish.

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However, Google announced plans to improve the classification and distinction of cookies, and provide more visibility to the user, as well as cracking down more harshly on fingerprinting. The company highlighted the distinction between trackers that follow your behaviour within a particular website in order to serve more appropriate ads, and those that follow you around between different sites, building a broad picture of your behaviour.


Research carried out by Google suggested that restricting third party cookie ad targeting would result in up to 52 per cent loss in programmatic ad revenue for publishers. However, it remains to be seen whether this is fully underlined by the facts, or is a cynical marketing move by Google. While some publishers agreed with Google’s figures, others said they had been taken out of context and incorrectly interpreted.

When asked about the impact on publishers a Mozilla spokesperson said it conducted research with media organisations before it decided to introduce the change. "While acknowledging that there’s a negative revenue impact, publishers view this as a short term issue while online advertising catches up to the new reality," the spokesperson said. "In response to anti-tracking technology, many publishers even told us they are already developing alternatives to profile-based targeted advertising. Essentially, they view privacy as being in their long-term strategic business interests."

Either way, increased cookie blocking measures from a range of web browsers might push the evolution of profitable ad targeting models that don’t rely on third party cookies, such as next gen contextual targeting techniques being developed by some publisher and media agencies.

Updated September 3, 2019 18:46BST: Additional comment from Mozilla has been added

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