Canonicalization Series 2: Domain name to lower case

I will continue the series on canonicalization (I have a big post under draft, still adding points to it). I had started a thread at WMW about canonicalization where I saw a very interesting query today. It was about converting upper case domain name to lower case.

The query says,

The following is my current (simple) Mod rewrite, and I am still confused as to why the capitalisation in the domain doesn’t get forced to lower case.

I assumed that www.EXAMPLE.COM would be forced to www.example.com – doesn’t seem to work that way.

Is making upper case domain name to lower case part of canonicalization?
Certainly not. Let me allow the authority docs do the explanation,

example.com
Example.com
eXample.com
exaMple.com
examPle.com
exampLe.com
examplE.com
EXAMPLE.com
ExAMPLE.com
EXaMPLE.com
EXAmPLE.com
EXAMpLE.com
EXAMPlE.com
EXAMPLe.com
etc.

In the languages that utilize Latin characters (e.g., English, Finnish, German, Italian, etc.), each letter has two variants: upper case and lower case. The Internet’s basic DNS and hostname specifications provide that the upper-case and lower-case variants of each letter are considered to be equivalent. Thus, all the variant domain names in the above list are treated as the same domain name.

Since the lower case and upper case domain names are technically same we do not need to do canonicalization (also we are helpless, we are not able to do anything as the server variable is in lower case always). Canonicalization is needed for the URLs which can be technically different but are same for your domain. Example www.idealwebtools.com can be technically different from idealwebtools.com (without www) but currently represent the same document.

3 thoughts on “Canonicalization Series 2: Domain name to lower case

  1. Tony Lee

    >> I have a big post under draft, still adding points to it
    Waiting for it, I liked your post at WMW. This was one of the different part to handle.

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