Thanks for the suggestion!

I fully support the proposal above, I think it's really important that Piwik does the right thing by default.

I expect other browsers might also start to send DoNotTrack HTTP headers by default...

Would it be possible to add a fourth option, which is to lump all DNT users in a single bucket with any identifying information zero'd out? This would mean the IP of all DNT users would be 0.0.0.0 (obviously invalid), their Lat/Long would be 0,0 (in the Atlantic ocean, south of Ghana), etc.

That would give us more accurate stats as far as what pages are popular and how many eyeballs we're getting, while also preserving the privacy of the users.

I really like this idea: #3531 (comment)
Could you please consider that for the future?

Also as additional suggestion to "lump all DNT users in a single bucket" if this is not too intrusive:
Maybe regenerate the visitor ID on every visit (e.g. delete the Matomo cookie on browser close), so that we, on the one hand, gather anonymized data as explained in the referenced comment, but also can see every visitor as unique and not many visitors as a big lump.
My idea is that we respect the DNT choice as much as possible but still gather statistical data about those users without the possibility to track them long-term or store any personalized data.

Personally, I do not mind being tracked by Matomo (in contrast to Google Analytics, advertisement companies, ...), as I know that for the vast majority of Matomo installation the data is only accessible to the people behind that website (or Matomo if it is a hosted setup). Unfortunately, this is currently not possible using DNT. Instead, browser extensions are required for that.

@chris246 See #12001 for a newer discussion about this idea.

But I am afraid that this is an issue that is currently solving itself:

The DNT working group has finished their work (w3c/dnt@5d85d6c) and it seems like it's usage will decrease in the next time (e.g. Apple completly removed it from Safari)