I have a site with only a small number of visitors. Using the "days since last visit" dimension in Google Analytics I thought I could work out a flow of individual visitors from day to day:

Date     OS   Browser  Days Since  Res       Visitor Type 
20120413 Win7 IE8      0           1140x641  New Visitor
20120815 Win7 IE8      123         1366x768  Returning Visitor
20120827 Win7 IE8      12          1366x768  Returning Visitor
20121019 Win7 IE8      51          1366x768  Returning Visitor
20121024 Win7 IE8      4           1249x702  Returning Visitor
20121026 Win7 IE8      1           1366x768  Returning Visitor

Based on the dates / days since info these visits are all from the same visitor (there are no other IE8 / Win 7 visitors within the relevant 24 hour buckets) but the screen resolution is different and so I question the data.

Is the resolution value in analytics based on some system value, or is it possible for analytics to report different resolutions depending on something as arbitrary as e.g. the browser window size?

EDIT: From GA docs it appears that this IS intended to be screen resolution; unless the DOM value from IE8 is different to what GA thinks it should be?

  • Does Analytics detect and save the "screen" resolution? I'd think that's the window size of the browser, so it was just resized?
    – marekful
    Commented Jan 4, 2013 at 14:45
  • Edited my post. Pretty sure it is screen resolution. Commented Jan 4, 2013 at 15:22
  • Well, it's absolutely possible to detect the screen size with JS and GA uses that... However resolutions in your example don't seem standard, especially 1140x641 and 1249x702 so I'd argue that GA passes window.innerHeight/Width instead of screen.availHeight/Width back to its server, this, however, is only an assumption.
    – marekful
    Commented Jan 4, 2013 at 15:52
  • It's way old but this comment: googleanalyticsguide.sureshchowhan.com/2007/11/… shows someone who asked Google and was told that analytics uses screen.width. I suppose it could have changed but googling has not revealed any mention of such. Commented Jan 5, 2013 at 8:18

1 Answer 1


Turns out multiple resolutions from a single visitor/browser is completely possible. Google Analytics asks the browser for the screen.width variable, which IE (and apparently Firefox) change when the user zooms in.


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