What is the format of Minecraft.net account names?

What is the format of Minecraft.net account names?

The information I have a use for is:

• what characters are permitted or prohibited?
• what is the maximum length?
• are they always treated as case-insensitive?

However, a complete, exact definition of the allowed format would be appreciated.

Solution 1:

The username must be between 3 and 16 characters (inclusive).

The characters permitted are :

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_

Usernames are case-sensitive in games (above your head), but when logging in using the username, whether is it in caps or not, will still work.

Solution 2:

Trying to register with an illegal character gives an error and mentions the following as allowed:

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_

And the longest username I could register was 'thisisalongusern'