Case Sensitive URLs, Duplicate Content & Link Rel Canonical

[allianzireland]

I have a site where URLs are case sensitive. In some cases the lowercase URL is being indexed and in others the mixed case URL is being indexed. This is leading to duplicate content issues on the site.

The site is using link rel canonical to specify a preferred URL in some cases however there is no consistency whether the URLs are lowercase or mixed case. On some pages the link rel canonical tag points to the lowercase URL, on others it points to the mixed case URL.

Ideally I'd like to update all link rel canonical tags and internal links throughout the site to use the lowercase URL however I'm apprehensive!

My question is as follows:

If I where to specify the lowercase URL across the site in addition to updating internal links to use lowercase URLs, could this have a negative impact where the mixed case URL is the one currently indexed?

Hope this makes sense!

Dave

[Hutch42]

While you might see a small down tick in the beginning as Google indexes and updates, overall you should not suffer any long term negative effects from standardizing your URI structure.

[RyanPurkey]

In addition to using rel=canonical for the lowercase version of your URLs you should also consider implementing redirection from uppercase to lowercase.  A regex expert should be able to write the redirect script you'll need to add to your .htaccess file in order to change upper to lowercase. Cheers!

[allianzireland]

Thanks Hutch and Ryan, great answers and exactly what I need. Appreciate it!