> screen brightness, memory amount, current volume and if I'm wearing headphones
None of those are likely to change when you navigate from one website to another, with tracking/ads disabled, which is what they want to be able to track. Otherwise they'd just use their cookies.
One device visits a site where you sell ads. A minute later, an unknown device with identical battery, volume, headphone, brightness, model number, browser version, and boot time to the second arrives on another site you run ads on. There's a pretty good chance they're related, because the odds of all those being the same plus those two sites and recent timings involved is rather low: https://coveryourtracks.eff.org/
Plus it doesn't have to be perfect. It just has to be good enough in bulk to sell.
None of those are likely to change when you navigate from one website to another, with tracking/ads disabled, which is what they want to be able to track. Otherwise they'd just use their cookies.
One device visits a site where you sell ads. A minute later, an unknown device with identical battery, volume, headphone, brightness, model number, browser version, and boot time to the second arrives on another site you run ads on. There's a pretty good chance they're related, because the odds of all those being the same plus those two sites and recent timings involved is rather low: https://coveryourtracks.eff.org/
Plus it doesn't have to be perfect. It just has to be good enough in bulk to sell.