Basically WTF-16 is any sequence of 16-bit integers, and is thus a superset of UTF-16 (because UTF-16 doesn't allow certain combinations of integers, mainly surrogate code points that exist outside of surrogate pairs).
Then WTF-8 is what you get if you naively transform invalid UTF-16 into UTF-8. It is a superset of UTF-8.
This is very useful when dealing with applications like Java and Javascript that treat strings as sequences of 16-bit code points, even though not all such strings are valid UTF-16.
> Basically WTF-16 is any sequence of 16-bit integers, and is thus a superset of UTF-16 (because UTF-16 doesn't allow certain combinations of integers, mainly surrogate code points that exist outside of surrogate pairs).
If WTF-16 is the ability in potentia to store and return invalid UTF-16 without signalling errors, I don't know that there's any actual UTF-16 system out there to the possible exception of… HFS+ maybe?.
Basically WTF-16 is any sequence of 16-bit integers, and is thus a superset of UTF-16 (because UTF-16 doesn't allow certain combinations of integers, mainly surrogate code points that exist outside of surrogate pairs).
Then WTF-8 is what you get if you naively transform invalid UTF-16 into UTF-8. It is a superset of UTF-8.
This is very useful when dealing with applications like Java and Javascript that treat strings as sequences of 16-bit code points, even though not all such strings are valid UTF-16.