Do query string case differences affect whether a URL is Canonical?

Question

If I have two URL's where the only difference is the case of the query string:

• http://example.com?param=TEST

• http://example.com?param=test

Are they both considered equal by search engines? I know the rest of the URL is case sensitive but I want to confirm that this is also true of the query string.

Solution 1

URLs that differ in case in the query string are different URLs to search engines. They are not considered equal and would need canonical tags or redirects to tell search engines which you prefer.

Different parts of the URL are different in terms of case sensitivity:

• Protocol (http) -- case insensitive
• Host name (example.com) -- case insensitive
• Path (/folder/document.html) -- case sensitive
• Query string (?foo=bar&fuzz=bat) -- case sensitive

Solution 2

Yes, all parts of URL after the domain name are case sensitive.

Also, query string case is important not just for search engines but it may be important for your server as well.

You may have the following download link:

http://example.com?download=/myVideos/CaseSensitiveVideo.mpeg

Comments

[Derecho]

Percent encoding is case insensitive, i.e. %7e and %7E are equivalent. The preferred form is uppercase. All of the rules on what is or is not case-sensitive are in RFC 3986.

[Stephen Ostermiller]

It is true that percent encoding is case insensative, although I'm not sure if search engines handle that correctly. My guess is that a canonical tag would help for SEO in that case.

[Derecho]

I'm pretty sure that Google has got it right. I can't say anything for any other search engine.