Online privacy campaigners on Tuesday said they had filed hundreds of complaints against websites and platforms in Europe over violations of rules on cookies, the files that track user activity.
The Austria-based group NOYB (None of Your Business) said 422 complaints had been filed with 10 data protection authorities and promised to make separate complaints against big players such as Amazon, Facebook, Twitter and Google.
The group had presented 516 companies with written warnings in May over their use of pop-up banners asking users to consent to "cookies", giving them one month to conform to EU rules.
The group said at the time the pop-ups did not give the user a simple "yes or no" choice over data collection that the law required.
In a statement on Tuesday, the NGO said there had been improvements on many websites, noting that almost half the violations had been fixed.
Many websites added a "reject" button or stopped using different colours for both buttons, a trick that encourages users to click on "accept".
"Some major players like Seat, Mastercard or Nikon have instantly changed their practices," said Max Schrems of NOYB, an Austrian activist who has notched up a series of legal victories over online privacy, including scuppering major EU-US data exchange arrangements.
"However, many other websites have only stopped the most problematic practices."
He said some had added a reject option but made it hard to read, adding that some website owners were still resisting the idea.
The activist group said major websites including Amazon, Twitter, Google and Facebook had refused to cooperate.
"Some openly argue that it would be legal to manipulate users into clicking 'okay'," said Schrems, promising to bring cases against them.
To stop what it calls the "cookie banner terror", NOYB aims to scan, review, warn and enforce the law on up to 10 000 websites within one year.
Statistics published in May by NOYB showed that only three percent of online users wanted "cookies", but more than 90% said yes to them as they could not reject them easily.