libUTF8
A super simple, super small, MIT-licensed UTF-8 library written in C11. Learn about UTF-8 over on Wikipedia!
Now if you've read the Wikipedia article, you'd know that since 2003 characters that were encoded to have 5 or 6 bytes are technically deprecated. Good news! libUTF8 still supports them! 👍
Want to use libUTF8? Neat! Just drop utf8.h and utf8.c into your project
and you're good to go!