There's actually two levels of jeopardy here: 1/ Treating a string as an array of bytes will give an invalid result if the string unless the string is simple a

There's actually two levels of jeopardy here: 1/ Treating a string as an array of bytes will give an invalid result if the string unless the string is simple ascii (or an equivalent encoding where each byte has a clearly defined standalone meaning); in particular, just reversing a UTF-8 string in this way will give an invalid answer - ie a string that isn't even valid UTF-8. 2/ The fix for (1) is to convert your string into an array of Unicode code points and reverse that … except that is also broken, because combining characters will now not associate correctly, as per other answers in this thread. Coding your way out of problem (2) in a robust and sensible way is, I suggest, a significant challenge.