UTF-8000 Extends UTF-8 to Encode Any Codepoint, No Matter How Large
UTF-8000: Unlimited UTF-8
A fun proposal called UTF-8000 stretches UTF-8 to support arbitrarily large codepoints by striping start bits across continuation bytes. It keeps ASCII as a subset, preserves self-synchronization and self-punctuation, and introduces no special cases beyond those inherited from UTF-8. A reference implementation is available via pipx install UTF-8000. Not affiliated with the Unicode Consortium.
The main contribution of UTF-8000's specification is clarity on splitting the highest bits of the first byte of UTF-8 code units into self-synchronization bits and start bits, and then making it clear how to stripe the start bits across the continuation bytes if needed, to achieve arbitrarily large code units.