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Next year, Alphabet Inc's Google plans to phase out technology in its Chrome browser that lets other companies track users' web browsing . But that does not mean you will see irrelevant ads, or that the pair of shoes you have been eyeing will stop following you around the web.
Here is why Google is making the move, the backlash it has generated and how advertisers plan to personalise ads even after the company kills off a technology known as third-party cookies.
Privacy concerns
Severe data breaches early last decade led to ground breaking privacy laws, in place since 2018 in the European Union and California, that impose significant fines on violators.
The laws ushered an end to the era of big tech companies tracking users' every move - often without permission - and sharing that data however they wanted with other businesses. Google, Apple Inc, Facebook Inc and nearly every other large internet company has become more explicit in allowing users to control what the companies know about them.
Browser wars
Cookies are a foundation of the web, allowing you to visit a news publisher without entering log-in credentials each time, for example.
Also Read | How a privacy tool detects what websites are tracking you
But privacy activists say companies that develop online ad technology abuse cookies by tracking users across many websites and letting brands use the data to target ads.
Apple's Safari, Mozilla's Firefox and upstarts such as Brave have been at the forefront of restricting that practice, and now Chrome, the global market leader with about 60% share, is catching up.
For years, online ad technology companies including Google could tell a shoe retailer to personalise an ad to someone reading a Reuters.com article after having tracked that person the week before researching a shoe on Nike.com and checking for a specific color on FootLocker.com.
Under these new policies, that tracking across multiple websites is unfeasible.
Common interests
As an alternative, Google is testing a way for businesses to target ads to clusters of consumers who have similar interests, which it says would be more private because it hides individual users in a crowd.
Also Read | Facebook to provide data on targeted political ads to researchers
The technology, part of a project called the Privacy Sandbox, would use an algorithm to group people according to their common web browsing. Each group would have a minimum membership, so individuals can't be identified.
Brands could target their ads to a cluster interested in buying a car, for example, rather than relying on cookies that have tracked specific users across car-buying websites.
Big trade groups representing advertisers have called on Google to delay phasing out cookies until an alternative proves suitable . Google said in January that its tests show the clustering system could be effective.
Antitrust accusations
The UK's Competition and Markets Authority in January began investigating whether restricting cookies on Chrome will help Google increase its dominance in the online ad industry.
Critics contend Google is banning rivals from building gigantic profiles on users, while developing for itself features in Chrome to continue to add to such dossiers.
Google in a blog post on Wednesday disputed that notion. The company vowed not to develop work arounds for itself, and committed to continue allowing targeting ads based on data that companies receive directly from consumers.
Other options
Other systems proposed by rivals to Google ad technology include one from Trade Desk Inc that relies on encrypted copies of email addresses that people use to log on to websites. The Washington Post said in December it would adopt The Trade Desk's tool, called Unified ID 2.0.
It is also possible that showing someone ads based on activities they undertook on another website will grow unpopular. Before cookies led to advances in targeting, ads more commonly were related to surrounding content, so a video about vaccines would feature ads from medical fields.
