For to the following URLs:


I'm showing the same content. Can this hurt SEO? I understand that theoretically it can, but does Google really penalize such cases and categorize it as duplicate content?

If so, would you advise on doing a 301/302 redirect or adding a rel="cannonical" to the lower case?

2 Answers 2


I agree with Zistoloen’s answer in that you should use rel-canonical or 301-redirects. However, I don’t agree that rel-canonical is the best practice.

If possible, you should use 301-redirects.

rel-canonical only works for search engines that support this link type keyword (which are not all search engines).

301-redirects work for everything and everyone. All search engines, all users, all tools.

Think, for example, of bookmarking services: if you’d use rel-canonical, some users might bookmark the uppercase variant, some the lowercase variant. If you 301-redirect, everyone would bookmark the same URL. Think of caches. Think of archives. Think of the "visited link" decoration. There are countless examples why it’s better to have a "forced" canonical URL (= 301 redirect) for a resource than just a recommendation (= rel-canonical).

Search engines need to differentiate upper and lower case in URLs, as there can be different pages whose URLs only differ in case. Now, if you have several URLs for the same page, search engines won’t "penalize" you. Assuming that they recognize that it’s duplicate content, they‘ll simply choose one of these URLs. But better be explicit here. Use 301-redirects, if possible; if not, use rel-canonical.

  • Can't the 301 cause losing some of the link juice? Say if I have a link to mydomain.com/Page which is 301 redirected to mydomain.com/page won't I lose like 10-15%?
    – Noam
    Commented Nov 5, 2013 at 18:14
  • Nobody knows the percentage but yes, you lose some link juice through a 301 redirect.
    – Zistoloen
    Commented Nov 6, 2013 at 9:36
  • @Noam: But you’d only "lose" anything if the redirected page was indexed/ranked before. If there is one "forced" canonical URL for a page from the beginning, you’ll never lose anything. Users don’t link to the other variant (as their browsers redirect them automatically), search engines don’t index the other variant, etc.
    – unor
    Commented Nov 6, 2013 at 10:38

Same URLs with lower case and upper case are two different URLs for search engines (thus Google). Therefore, it can be cause duplicate content issues which is very bad for SEO.

A good practice is to use the rel="canonical" tag to tell to search engines which version of your page (=which URL) is the one to follow (how to use this tag on Google support).

However, 301 redirecting upper case URL to corresponding lower case URL can be a good approach if you use a Linux server because Linux servers are case-sensitive and generate 404 errors.

  • I understand this theoretically, but are there documented cases that Google actually doesn't understand these cases? Also - any claims as to rel=cannonical vs. redirect?
    – Noam
    Commented Nov 4, 2013 at 18:37
  • I have edited my answer.
    – Zistoloen
    Commented Nov 4, 2013 at 19:21

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