I visit the Information Commissioners Office (ICO) https://ico.org.uk/ which is the commissioner who is in charge of things like GDPR and cookies in the UK.
They have the option to opt out of cookies, which I duely did. I then refreshed and I could still see cookies being load for Google Analytics.
A few days later I returned and the cookie must have expired. Were my original findings due to browser cache? And if so, is there a way to force browsers to forget cookies? I would find this more compliant with the users wishes.
I think if a cookie can expire, then perhaps you could set the expiry date to now when a user opts out. Or set the cookie to 1900 or something similar so it expires. Or set it to null if that would make a difference.
Is it possible to remove a cookie instantly when a user opts out, or is that entirely down to the browser settings?