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:
John Mueller AskGooglebot Transcript
Today we have a question from Hamza on Twitter who asks: Does upper or lowercase in URLs matter? Well, thank you for asking. URLs are the basis of all websites. So it’s good to double check your assumptions. By definition, URLs are case sensitive. And also things like slashes at the end do matter.
So technically, yes, these things matter. They make URLs different. If a website still shows the same content in these cases, search engines will try to figure it out on their own. And usually that works out well. But it’s not always ideal.
For example, search engines will try to crawl all variations of a URL that they find. This can make it a bit slower for them to find other useful content on your website. Also, when search engines find multiple distinct URL showing the same content, they have to decide which of these URLs to keep, we call this canonicalization.
It doesn’t change ranking. But our systems might choose a URL that you wouldn’t have chosen. Another place where the exact URL plays a role is robots.txt. In the robots.txt file, you can signal which parts of a website shouldn’t be crawled.
The robots.txt file also uses the exact URL. So if you have entries there, which refer to one version of a URL, they would not apply to other versions of that URL. It’s rare that we see this cause problems so using internal linking to link to a consistent version makes your preference clear. Adding a link rel=canonical element also helps to confirm that and encourages search engines to focus on that version.
So in short, upper or lowercase does matter for URLs. It’s a good practice to be consistent in how you use them, but it’s usually not that critical for a website. I hope this helps to answer this question. See you on the next episode of Ask Googlebot for more questions and more answers.