In an Ask Googlebot session, one SEO professional was concerned about upper and lowercase URLs.
They asked if upper vs. lowercase URLs mattered for SEO?
John explained that because URLs form the basis of your entire website, yes, it absolutely does matter when it comes to upper case vs lower case for URLs.
He said that yes, by definition URLs are case sensitive. Also, certain things like trailing slashes on these URLs matter as well.
If a website shows the same content on these URLs, it could be considered duplicate content. But, even so, the search engine has to decide the URL they want to keep.
This process is what Google refers to as canonicalization.
This doesn’t affect ranking, but Google’s systems may choose a URL that was not specified or was not chosen by the SEO professional.
To minimize the impact that having multiple duplicate URLs like this can cause, John recommends using the rel=canonical tag as a method of canonicalization, and way to encourage search engines to focus on the one URL you want them to focus on.
You can watch the entire video below: