This post is a really good illustration of UTF-8. Very clear! The key brilliance of the design is not only the embedding of ASCII in UTF-8, but the fact that nothing in ASCII can appear anywhere else UTF-8, and more generally that no UTF-8 character can appear as a substring of another character’s encoding. That means that all the byte-oriented libc string functions just work. I wrote this up recently in a StackOverflow answer with some examples: https://stackoverflow.com/a/69756619/659248