Thanks for the feedback, Federico!  That actually helps a lot and also helps confirm what our programmer has just done (which is changed all the canonical tags to the uppercase URL).  I guess now we'll play the waiting game and see if Google reduces the number or duplicates after it's next crawl.

Thanks again!

Hi MOZ, I was hoping that someone could help shed some light on an issue I'm having with URL structure and the canonical tag.

The company I work for is a distributor of electrical products and our E-commerce site is structured so that our URL's (specifically, our product detail page URL's) include a portion (the part #) that is all uppercase (e.g: buy/OEL-Worldwide-Industries/AFW-PG-10-10).

The issue is that we have just recently included a canonical tag in all of our product detail pages and the programmer that worked on this project has every canonical tag in lowercase instead of uppercase.  Now, in GWT, I'm seeing over 20,000-25,000 "duplicate title tags" or "duplicate descriptions".

Is this an issue?  Could this issue be resolved by simply changing the canonical tag to reflect the uppercase URL's?  I'm not too well versed in canonical tags and would love a little insight.

Thanks!