What are the character limitations in naming a domain?

A domain name can have up to 59 characters. Domain names can only use letters, numbers, and hyphens (-). Spaces, punctuation marks, and other symbols are not allowed, and domain name cannot begin or end with a hyphen. IDN (International Domain Names) for .com, .info, .net, .org, .biz, .cc, .tv and .ws can contain ä, ö, and ü symbols.