The Information Commissioner’s Office (ICO) warned Google against a policy “U-turn” allowing advertisers to use “fingerprinting” technology, which involves cross-referencing device hardware and software information to uniquely recognise a user.

“Fingerprinting is not a fair means of tracking users online because it is likely to reduce people’s choice and control over how their information is collected,” the ICO said in a statement.

Unlike “cookies” — the data tags that allow companies to trace an internet user’s path on the web — digital fingerprinting relies on data from the surfer’s software or device, making it harder to control.

According to the ICO, under Google’s changed terms of use published on Wednesday, the digital footprint could “replace the functions of third-party cookies” when it comes into effect on February 16, 2025.

“We think this change is irresponsible. Google itself has previously said that fingerprinting does not meet users’ expectations for privacy, as users cannot easily consent to it as they would cookies,” the ICO said.

Additionally, it is harder to make changes to or erase a digital fingerprint, unlike cookies which can be “wiped”, according to the data privacy watchdog.

“We are continuing to engage with Google on this U-turn,” added the ICO, warning that “businesses do not have free rein to use fingerprinting as they please”.

“Like all advertising technology, it must be lawfully and transparently deployed –- and if it is not, the ICO will act.”

“Businesses must give users fair choices over whether to be tracked before using fingerprinting technology, including obtaining consent from their users where necessary.”

Data like “IP addresses are already commonly used by others in the industry today”, a Google spokesperson told AFP.

The American tech giant “continue(s) to give users choice whether to receive personalised ads, and will work across the industry to encourage responsible data use”, the spokesperson added.