utf16 is more efficient if you have non-english text, utf8 wastes space with long escape sequences. but the real reason to always use nvarchar is that it remains sargeable when varchar parameters are implicitly cast to nvarchar.
UTF-16 is maybe better if your text is mostly made of codepoints which need 3 UTF-8 code units but only one (thus 2 bytes) UTF-16 code unit. This is extremely rare for general text and so you definitely shouldn't begin by assuming UTF-16 is a good choice without having collected actual data.
The old defense of 16-bit chars, popping up in 2026 still! Utf8 is efficient enough for all general purpose uses.
If you're storing gigabytes of non-latin-alphabet text, and your systems are constrained enough that it makes a difference, 16-bit is always there. But I'd still recommend anyone starting a system today to not worry and use utf8 for everything.j
What do you mean with non-english text? I don't think "Ä" will be more efficient in utf16 than in utf8. Or do you mean utf16 wins in cases of non-latin scripts with variable width? I always had the impression that utf8 wins on the vast majority of symbols, and that in case of very complex variable width char sets it depends on the wideness if utf16 can accommodate it. On a tangent, I wonder if emoji's would fit that bill too..
I am not sure if you mean me, as I just asked a question. I wonder what the best way is to handle this disparity for international software. It seems like either you punish the Latin alphabets, or the others.
> I wonder what the best way is to handle this disparity for international software. It seems like either you punish the Latin alphabets, or the others.
there are over a million codepoints in unicode, thousands for latin and other language agnostic symbols emojis etc. utf-8 is designed to be backwards compatible with ascii, not to efficiently encode all of unicode. utf-16 is the reasonably efficient compromise for native unicode applications hence it being the internal format of strings in C# and sql server and such.
the folks bleating about utf-8 being the best choice make the same mistake as the "utf-8 everywhere manifesto" guys: stats skewed by a web/american-centric bias - sure utf-8 is more efficient when your text is 99% markup and generally devoid of non-latin scripts, that's not my database and probably not most peoples
> sure utf-8 is more efficient when your text is 99% markup and generally devoid of non-latin scripts, that's not my database and probably not most peoples
I think this website audience begs to differ. But if you develop for S.Asia, I can see the pendulum swings to utf-16. But even then you have to account for this:
«UTF-16 is often claimed to be more space-efficient than UTF-8 for East Asian languages, since it uses two bytes for characters that take 3 bytes in UTF-8. Since real text contains many spaces, numbers, punctuation, markup (for e.g. web pages), and control characters, which take only one byte in UTF-8, this is only true for artificially constructed dense blocks of text. A more serious claim can be made for Devanagari and Bengali, which use multi-letter words and all the letters take 3 bytes in UTF-8 and only 2 in UTF-16.»¹
In the same vein, with reference to³:
«The code points U+0800–U+FFFF take 3 bytes in UTF-8 but only 2 in UTF-16. This led to the idea that text in Chinese and other languages would take more space in UTF-8. However, text is only larger if there are more of these code points than 1-byte ASCII code points, and this rarely happens in real-world documents due to spaces, newlines, digits, punctuation, English words, and markup.»²
The .net ecosystem isn't happy with utf-16 being the default, but it is there in .net and Windows for historical reasons.
«Microsoft has stated that "UTF-16 [..] is a unique burden that Windows places on code that targets multiple platforms"»¹
the talk page behind the utf-16 wiki is actually quite interesting. it seems the manifesto guys tried to push their agenda there, and the allusions to "real text" with missing citations are a remnant of that. obv there's no such thing as "real text" and the statements about it containing many spaces and punctuation are nonsense (many languages do not delimit words with spaces, plenty of text is not mostly markup, and so on..)
despite the frothing hoard of web developers desperate to consider utf-16 harmful, it's still a fact that the consortium optimized unicode for 16-bits (https://www.unicode.org/notes/tn12) and their initial guidance to use utf-8 for compatibility and portability (like on the web) and utf-16 for efficiency and processing (like in a database, or in memory) is still sound.
Interesting link! It shows its age though (22 years), as it makes the point that utf-16 is already the "most dominant processing format", but if that would be the deciding factor, then utf-8 would be today's recommendation, as utf-8 is the default for online data exchange and storage nowadays, all my software assumes utf-8 as the default as well. But I can't speak for people living and trading in places like S.Asia, like you.
If one develops for clients requiring a varying set of textual scripts, one could sidestep an ideological discussion and just make an educated guess about the ratio of utf-8 vs utf-16 penalties. That should not be complicated; sometimes utf-8 would require one more byte than utf-16 would, sometimes it's the other way around.
The non sargeablilty is an optimizer deficiency IMO. It could attempt to cast just like this article is doing manually in code, if that success use index, if it fails scan and cast a million times the other way in a scan.
implicit casts should only widen to avoid quiet information loss, if the optimizer behaved as you suggest the query could return incorrect results and potentially more than expected, with even worse consequences
It should not return incorrect results, if the nvarchar only contains ascii it will cast perfectly, if it doesn't then do the slow scan path, it's a simple check and the same work its doing for every row in the current behavior except one time and more restricted. Can you give me an example of an incorrect result here?
I am not talking about the default cast behavior from nvarchar to varchar, but a specific narrow check the optimizer can use to make decision in the plan of ascii or not with no information loss because it will do the same thing as before if it does not pass the one time parameter check.
By far the most common cause of this situation is using ascii only in a nvarchar because like say in this example the client language is using an nvarchar equivalent for all strings, which is pretty much universal now days and that is the default conversion when using a sql client library, one must remember to explicitly cast rather than the db doing it for you which is the expected behavior and the source of much confusion.
This would be purely an optimization fast path check otherwise fall back to the current slow path, correct results always with much faster results if only ascii is present in the string.
