Not every string uses the same amount of content bits per character. If you use only numbers you use 3 1/2 bit per character, if you use only numbers, uppercas

Not every string uses the same amount of content bits per character. If you use only numbers you use 3 1/2 bit per character, if you use only numbers, uppercase letters and some limited punctuation it’s 5 1/2 bits per character. Otherwise it’s 8 bits per character but that’s a waste because most of the characters you can then represent can’t be used in a URL.