I was recently asked the difference between how Google handles Urchin Tracking Module (utm) tagged URLs and other, nonsensical URL strings e.g. why are URLs like www.site.com/thingy?thing1&dullID9283 no use for SEO, but it’s OK to have a Google tagged URL such as www.site.com/thingy?utm_source=value1&utm_medium=value2&utm_campaign=value3.
It’s not a new topic but it reminded me that there isn’t much explanation out there, so here goes…
Here’s how spiders handle things:
Google spiders do recognise strings after the “?”, but handle them by not expending any energy on digging deeper.
This is because there are so many possible permutations in ecommerce sites that a crawl could take days.
So, the spider does recognise them, but doesn’t usually follow them.
That is why ecommerce URLs like www.domain.com/product?prod=hiticket&ID=1234 are poor.
Google doesn’t care that www.domain.com/product is different to www.domain.com/product?prod=hiticket&ID=4321 or www.domain.com/product?prod=loticket&ID=1234.
It knows they may be, but won’t bother looking to find out- so its more a matter of content being ignored than being percieved as duplicate.
However when a Google spider encounters a URL containing an Urchin Tracking Module tag (utm) it will happily follow it.
Here’s how analytics handles things:
When someone actively clicks on a utm tagged URL, that click is an entirely seperate event from a site crawl.
The click triggers a reportable event because the tagging tells it to.
A spider crawl doesn’t trigger a reporting event because that is the nature of the spider.
Google has made good provision so that there is no confusion between how a short, organically crawled URL such as www.site.com/thingy is handled, and the longer click-enabled utm URL such as www.site.com/thingy?utm_source=value1&utm_medium=value2&utm_campaign=value3 is handled.
The URL builder at http://www.google.com/support/googleanalytics/bin/answer.py?hl=en&answer=55578 will definitely allow you to see how any analytics enabled campaign is performing.
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