Difference in reported numbers between Piwik and Google Analytics


I’m using Piwik since a couple days now. I’m archiving with a crontab.

I have noticed that there is a big difference between what Google Analytics and what Piwik report.

For instance for the 6th January following numbers (rounded) are reported:

Piwik unique visitors: 564.000
Piwik visits: 637.000
GA unique visitors: 759.000
GA visits: 1.106.000

I wonder where the difference could come from. Is there something fundamentally different in how users are tracked?

Thank you very much!

Piwik version: 3.0.0
MySQL version: 5.6.27
PHP version: 7.0.8-0ubuntu0.16.04.3

SOLUTION: It seems the difference came from do-not-track being enabled in Piwik. After disabling do-not-track the real time visitor count matches (5 minute interval) the one from GA.