Global Privacy Control, honoured properly

Global Privacy Control is a header a browser sends to say the person using it does not want to be tracked. Unlike Do Not Track before it, it has legal weight in several places, and it is easy to honour badly.

Honouring it badly looks like this: record the visit, note the preference, then filter those rows out of the reports. The numbers come out right and the data is still there.

Honouring it properly means the check happens before anything is written. There is no row to filter and nothing to delete later, because nothing was created.

The difference only shows up when somebody asks what you hold about them, and the honest answer is that you never held anything. That is a much better conversation than explaining your exclusion filters.