Difference in Piwik and Google Analytics numbers

I installed Piwik few months ago. In order to see what’s happening I track the data both on Piwik and Google Analytics. However, the numbers in GA are significantly higher than those in Piwik.
Below is the data which am getting form both the analytical tool -

User/Visitors : - GA - 12550, Piwik - 11782
Visit/Session :- GA - 22141, Piwik - 14584
Returning Visit/session :- GA - 12554 , Piwik - 8697
Bounce Rate : - GA - 22% Piwik - 16%

What might lead to GA numbers being significantly higher than Piwik. As the code is pasted in all the pages of the website.

Hi there,

That’s totally normal, reasons can be very different, it can be either robots which are taken into account in GA but not in Piwik, it can also be that Piwik is not counting visitors and visits the same way as GA in some specific cases, it can be your server which may have some downtime, it can be the donottrack option set on some browser, extensions such as adblock etc.
What is the most important is to analyze trends from both analytics packages in order to make a decision.
In some months, weeks, days, you may have more data into Piwik than GA too.