Are there any places where utf8 vs. utf-8 vs. UTF8 vs. UTF-8 makes a difference? [closed]

Question

In many different code environments' official documentation I see UTF-8 expressed either as upper- or lower- case, and also with and without the dash. Are there any places where one or the other is important to use?

Some places where these strings are found include:

• The PHP manual in reference to header() arguments (HTTP headers)
• The PHP manual in reference to PHP function arguments
• The PHP manual in reference to internal configuration
• The MySQL manual in reference to configuration
• Python 2 code encoding declaration
• Bash locale configuration
• HTML meta tags
• XML doctypes

Answer 1

This is indeed wildly different. One place will accept only one form; the other place will only accept the other.

Listing here which is correct in which situation is not a good idea - it would be a huge and pointless open-ended list. Simply always look up in the respective documentation which form(s) is/are accepted for the specific situation.

Answer 2

The official registry of encodings defines the names as case-insensitive and the spelling as UTF-8 (UTF8 isn’t even a valid alias). It is highly unlikely that any software that can deal with UTF-8 would not recognize the name UTF-8. So in all places, it is important to use UTF-8 and not UTF8.

Since the names are case-insensitive, documentation may use any casing. Software that imposes case restrictions on them would be seriously broken, and I don’t see why would assume that such software exists. Variation in documentation does not mean that some specific casing of letters must be used.