I think it's also more space efficient when dealing with foreign languages primarily. For plain text, yes. UTF-16 covers the Basic Multilingual Plane in 2 byte

I think it's also more space efficient when dealing with foreign languages primarily. For plain text, yes. UTF-16 covers the Basic Multilingual Plane in 2 bytes per character, UTF-8 covers the BMP in at most 3 bytes per character. However, since most (web) content is dominated by markup in ASCII, which is 1 byte per character in UTF-8 and 2 bytes per character in UTF-16, UTF-8 typically wins even with Asian scripts. Taking some random zh Wikipedia page in UTF-8: curl "https://zh.wikipedia.org/wiki/威蘭運河" | wc -c 78543 curl "https://zh.wikipedia.org/wiki/威蘭運河" | wc -m 71003 So, that's 1.11 bytes per character on average, compared to at least 2 bytes per character if it was encoded in UTF-16. (Of course, adding compression is going to diminish the differences anyway. A very primitive compression algorithm in such cases would be recoding your UTF-16 to UTF-8 :p.)