Maybe they didn't want to be early adopters of what could turn out to be a second fad like UCS-2 was the first time.

What's depressing about the saga of utf8 adoption is that it's such an obvious solution. The ISO2022 standards used the principle since the 70s, and programmers of the era were widely accustomed to extending 8 bit instruction sets to multibyte instructions.

It's one of those cases where you need to hit your head hard and repeatedly until you bite the bullet and accept that the cost of multibyte (for example, strlen() different from character count, need to parse to seek etc.) are trivial compared to the benefits.

UTF8 is only superior in encoding the american keyboard (7 bits of ascii). All the latin letters map to 1 byte encodings. This is why UTF8 wasn't universally hailed to begin with.

Countries like Japan had already solved encoding differently while US was still using ASCII. (See JIS encoding).

As time passed tho, the byte savings matter less. Also combined with transfer compression makes the encoding size differences negligible.

> UTF8 is only superior in encoding the american keyboard (7 bits of ascii). All the latin letters map to 1 byte encodings.

In practice, basic 7-bit ASCII characters dominate a lot of texts, even those in East-Asian languages, as all the markup and such around the actual text is almost always in plain ASCII. For example, if I request a Japanese document from a HTTP server then the HTTP headers, HTML tags, CSS is all in single-byte characters.

Of course, there are still many scenarios where UTF-16 "wins" in terms of size – especially with plain text – but real-world size comparisons tend to be a bit more tricky.

For example, for the current Wikipedia homepage of ja, zh, and ko:

    % file *
    ja-16.htm: HTML document, Unicode text, UTF-16, little-endian text, with very long lines (2709)
    ja-8.htm:  HTML document, Unicode text, UTF-8 text, with very long lines (2709)
    ko-16.htm: HTML document, Unicode text, UTF-16, little-endian text, with very long lines (2503)
    ko-8.htm:  HTML document, Unicode text, UTF-8 text, with very long lines (2656)
    zh-16.htm: HTML document, Unicode text, UTF-16, little-endian text, with very long lines (5589)
    zh-8.htm:  HTML document, Unicode text, UTF-8 text, with very long lines (5589)

    % ls -lh
    210K  ja-16.htm
    118K  ja-8.htm
    193K  ko-16.htm
    106K  ko-8.htm
    189K  zh-16.htm
    104K  zh-8.htm

The UTF-16 versions are all larger (and that's just the HTML, excluding the CSS, JS, etc).

I wrote a small script to count the number of "wide" multibyte characters:

    ja-8.htm  100,808 7-bit characters;  19,026 wide characters
    ko-8.htm  93,888  7-bit characters;  14,149 wide characters
    zh-8.htm  91,589  7-bit characters;  14,360 wide characters

It was higher than I expected, although not that surprising when looking at the source when you have things like:

    <div class="vector-page-toolbar">
        <div class="vector-page-toolbar-container">
            <div id="left-navigation">
                <nav aria-label="名前空間">

Your argument uses a website whose code was written by English speakers. There would still be ASCII but verbose element names like "vector-page-toolbar-container" would definitely be shorter both in utf-8 and in utf-16.

<div class=..> is still <div class=..>, no matter the language of the author. As is "background-color: #fff" in CSS. The UTF-16 is almost double the size, so you'd have to replace a lot of identifiers with 2 or 3 byte ones.

Plus many identifiers come from libraries, and when creating their own identifiers many people use either full English or partial English no matter what language (it was a huge mistake to not use English for many identifiers in my first programming job, as you will invariably end up with a mishmash of two languages).

But it is easy enough to verify this with some actual websites: https://www.rakuten.co.jp is 330K in UTF-8 and 625K in UTF-16, https://ameblo.jp is 104K in UTF-8 and 187K in UTF-16, baidu.com is 360K in UTF-8 and 717K in UTF-16, sina.com.cn: 455K, 854K, daum.net: 666K, 1.2M.

And all of that is only the HTML document; if we'd add up the CSS – where there's almost no possibility to use non-ASCII outside of class and ID names – and JavaScript – where the filesize is usually dominated by React or jQuery or whatnot – things would skew even more in favour of UTF-8.

I'm sure there are examples where a page served over UTF-16 is smaller, such as pages with very little markup (like e.g. HN), but that is the common case, even for websites exclusively written and for users of CJK languages. Someone who does not speak a word of English will save many bytes of data every day with UTF-8. There's a reason all those websites are served over UTF-8 and not UTF-16.

But for the sake of the argument, let's replace all class="...", id="..", and data-event-name=".." with strings of the same length consisting of "回". That grows the filesize from 118K to 151K, and ... it's still larger in UTF-16 with 207K. We could start replacing more stuff and eventually UTF-16 may win, maybe. But you have to use a lot of CJK. Let's use a random excerpt:

        <button
            id="回回回回回回回回回回回回回回回回回回回回回回回回"
            tabindex="-1"
            data-event-name="回回回回回回回回回回回回回回回回回回回回回回回回回回回回回回回回回回回回"

Has 91 7-bit characters and 60 multibyte ones (this includes indentation, which may not be represented 100% accurately here). If we do the math this is:

  UTF-8    91×1 + 60×3 = 271 bytes
  UTF-16   91×2 + 60×2 = 302 bytes

UTF-8 still wins.

And to repeat, there are certainly cases where UTF-16 is smaller. Markdown documents and other plain text files is an obvious one, but HTML is rarely one of them.

But imagine actually checking things before making a claim...

Also, HTTP tends to use gzip in-flight, and modern office document file formats also use compression, making any potential space savings for UTF-16 CJK text completely negligible in these common cases. UTF-8 and UTF-16 are basically the same size after compression[0].

[0] http://utf8everywhere.org/#asian

> But for the sake of the argument, let's replace all class="...", id="..", and data-event-name=".." with strings of the same length consisting of "回". That grows the filesize from 118K to 151

You're missing the point entirely, the amount of characters you used is enough for 2 or 3 sentences. This was not an example constructed in good faith.

How is it "bad faith" when I spent the time actually converting and checking the entire document?

Is there any particular reason to think HTML would be high on the list of things they thought about when they decided this? It's not like the world wide web had taken over everything yet…

I don't know the exact considerations at the time – I wasn't there, and at "only" 38 I'm too young to have lived through it. But the argument holds for many different formats and protocols, I just used HTML as it's common today and I could easily find content for it.

For example plain text emails still have considerable ASCII data in the headers, no matter which language you use to send them, and depending on the length of your email UTF-8 may be smaller than UTF-16. I just checked a very simple email in my inbox, and it has 165 lines of headers for 21 lines of actual email body text (plain email, no MIME). Even after removing the more modern headers (DKIM, X-Spam-, etc.) we're still left with 35 lines, or 1,886 bytes. The actual email text is 765 bytes, in basic English. If the email text was in CJK it would still be slightly over 1K smaller* in UTF-8 (4,181 bytes vs. 5,302).

Longer emails would be smaller in UTF-16. I don't know what the average works out to, but ~21 lines seems about average for an email, give or take.

UTF-8 is superior due to self-synchronizing features and the fact truncated or otherwise damaged sequences are obviously damaged, even if they use unknown characters.

ISO 2022 isn't beautiful solution like UTF-8 self sync encoding. Backward compatibility is also great (so called UTF FSS). It was designed by smart Plan9 people.

If Ken and Pike could design it in an afternoon, I'm sure even a standards committee could have done it in less than 5 years or so, the ideas are straight forward.

I would also argue that the fast sync with at most one character consumed is a good feature but not essential for adoption. Any byte-oriented Unicode packing scheme that can gracefully consume ASCII is better than multibyte, codepages sent out-of-band etc. etc.

I have asked myself the same question. However, I observed that the switch from UCS-2 to true UTF-16 was already very bumpy, with strange bugs and tons of edge cases that only got significantly better in Windows 8. A forced switch to UTF-8 would likely have broken ANSI strings.

Languages such as PHP didn't get true UTF-8 support until 2015, Python in 2008 (and that switch took a decade), and Java and JavaScript continue to use UTF-16 as default strings.

The wastefulness of UTF-16 is mostly remedied by Unicode Compression (SCSU), which can be much shorter than UTF-8 in languages like Hindi and Chinese.

How many Windows users do benefit significantly from using UCS-2 encoding, I wonder? Chinese and Hindi (along with Japanese, South Korean and various Arabic language) speakers would surely come close to outnumbering those of us using European alphabets (I gather that Cyrillic & Greek have single-byte encodings, but maybe they mostly use UCS-2 these days too?). On that basis it seems a reasonable choice as the default storage method for human readable strings. But if course a high percentage of strings don't exist for that purpose at all, at least not primarily - using UCS-2 for storing/ transmitting CSS or configuration files or of course source code for most languages is less justifiable.

Microsoft software supports UTF-16 (not only UCS-2) everywhere these days (yes, even in COM). But you can probably still find errors here and there.

I have no problem with saving text files in UTF-8 and normally do. I just wish SCSU was handled by COM by default as well and not only sometimes.

> Chinese and Hindi (along with Japanese, South Korean and various Arabic language) speakers would surely come close to outnumbering those of us using European alphabets

You are probably right. Just slightly off topic: Hindi speakers who use computers mostly seem happy enough with English-language forms, instructions, and technical documents. This is true of most Indian users who speak languages that use one of the Indic scripts. Actual non-English text is useful mainly for publications like newspapers, magazines, and books, which native speakers do prefer to consume in their own language.

The above is, of course, not counting the significant numbers of Indians who are quite comfortable using English for daily communication. These Anglophones are just like US speakers in their preferences and have no use for internationalization.

UTF-16 is simpler and more efficient to handle than UTF-8.

I feel like you're confusing it with UTF-32, which is fixed-length. UTF-16 is neither fixed-length, like UTF-32, nor compatible with the old ASCII encoding, like UTF-8.

The historical reasons of why UTF-16 exists are fully understandable, but by now it is clear that it's the worst of both worlds.

No, I'm fully aware of it being a variable-length encoding. Yet as such it is still simpler to work with than UTF-8. So if we are to use a variable-length encoding anyway then UTF-16 is a reasonable choice. It is not compatible with ASCII and old APIs, that's true, but I cannot judge how important this is. I guess that for some projects the efficiency of UTF-16 should outweigh the inconveniences of that incompatibility.

Can you explain in what way it is easier to handle than UTF-8? Most code that I've seen and looks easier just mishandles characters outside the basic multilingual plane. Thankfully, due to emojis being a thing, a lot of developers woke up to the fact that Unicode specifies more than 65536 characters.

UTF-16 is cheaper to decode. All CPUs have branch predictors, 99.99% of all UTF-16 strings don't contain any surrogate pairs.

For East Asian languages UTF-16 uses 50% less memory, these characters take 3 bytes in UTF-8, but only 2 bytes in UTF-16.

That's 33% less memory, or conversely, UTF-8 uses 50% more memory.

This is plain decoding of a trusted string:

    utf16 decode
      if (unit <= 0xD7FF || unit >= 0xE000)
        /* one unit */;
      else
        /* two units */
    utf-8 decode
      if (unit < 0xE0) {
        if (unit < 0xC0)
          /* one unit */
        else
          /* two units */
      }
      else if (unit < 0xF0)
        /* three units */
      else
        /* four units */

UTF-16 will take one comparison for all characters up to 0xD7FF; UTF-8 normally takes two. Same when encoding:

    utf16 encode
      if (value <= 0xFFFF)
        /* one unit */
      else
        /* two units */
    utf8 encode
      if (value <= 0x7FF) {
        if (value <= 0x7F)
          /* one unit */
        else
          /* two units */
      }
      else if (value <= 0xFFFF)
        /* three units */
      else
        /* four units */

(We can tune UTF-8 it to take one comparison for ASCII if we expect mostly ASCII.)

Things get even more complex when we are to read an untrusted string. In UTF-8 we have five byte types, invalid bytes, conditionally invalid bytes, and must recognize surrogates (as errors). In UTF-16 all 16-bit units are valid and there are only three unit types: character or surrogate, high or low. I once wrote a decoder for UTF-8/16 and here's my stats:

    UTF-8    : 13 byte types, 13 states, 10 actions
    UTF-16LE :  3 byte types,  4 states,  5 actions

utf-8 has an elegance that utf-16 lacks:

    utf-8 decode
      switch (std::countl_one(unit)) {
        case 0:
          /* one unit */
          break;
        case 2:
          /* two units */
          break;
        case 3:
          /* three units */
          break;
        case 4:
          /* four units */
          break;
        default:
          /* not code point boundary */
          break;
      }

Oh, thanks, this one is good. Must be rather fast on major platforms. But with this optimization UTF-8 still remains harder computationally than UTF-16.

I’m happy every time I see c++20 in the wild

Can you show some concrete instances of it being easier to work with compared to UTF-8? As far as I can see you gain variable length encoding (albeit in a potentially confusing way) while losing ASCII support and also not gaining the pure simplicity of UTF-32. Oh and also endianness, although personally that's probably never an issue I will run into.

(Please see my reply to a sibling comment.)

Perfect, thanks for the heads up!

> UTF-16 is simpler and more efficient to handle than UTF-8.

Only if you never go out of the basic multilingual plane. And then find out so many bugs when people start using emojis.

IIRC the attitude was that the "ASCII" versions of functions largely existed only for backwards compatibility, after all on NT[1] they're basically just wrappers that do character set conversion before passing through to the real Unicode (UCS2/UTF16) functions. The view was that if you want Unicode, you should use the real functions directly, which means 16 bit strings.

I think there was also some compatibility concerns, as Windows for a while only had a single global "ASCII" character set used by all apps[2], so you'd have issues with actual legacy apps expecting a real legacy code page breaking / having scrambled text if you tried to use UTF8 as the "legacy" encoding. Or the fun idea of an app that is clever enough to know that multibyte exists, but dumb enough to know they can only be one or two bytes long, and allocating buffers accordingly. I think there might have been some issues with how things like the clipboard handled text as well that assumed all "ASCII" apps used the same encoding. (Disclaimed: old memories of reading blogs, may be bollocks). At some point things must have been fixed so multiple character sets could be used though.

[1] But not on 9x, which was "ASCII" only, at least until late in the day when a Unicode compatibility library was created.

[2] The "Language for non-Unicode programs" as the Control Panel calls it.

The "A" stands for "ANSI", not "ASCII". Otherwise largely correct.

> and finally got the proper support in Windows 10

Not quite, you still can't use some features like longPathAware with the "ANSI" APIs. The preferred APIs for file paths are still the ones using wchar, although the UTF8 codepage is apparently the preferred method for non-path APIs and console IO, at least on the GDK.

> It seems the solution would be simple: once UTF-8 introduced (back in 1996!), add new "UTF-8" codepage, add new "SetDefaultCodepageToUnicode()" function, and tell everyone that wchar_t is legacy and should not be used anymore. They could probably do it in time for Windows XP!

IIRC, the problem was that a MBCS codepage could have a maximum of 2 bytes per character, while UTF-8 could need 3 or even 4 bytes per character. Legacy applications could have fixed-size buffers with space for only 2 bytes per character, and would break if the default codepage needed more than that.

> Instead, UTF-8 codepage was only introduced in Windows 7 (but had incomplete support), and finally got the proper support in Windows 10. That's a lot of time Windows programmers were forced to use UCS-2.

It appears to me that lately Windows hasn't been as obsessed with backwards compatibility as it had been in the past. They are also gradually allowing for more use of paths longer than MAX_PATH (260 characters), which are not accessible to legacy applications, and as everyone knows, the compatibility with 16-bit applications has been dropped some time ago.

That's a good point... so don't make it default!

Make "SetThreadLocale" or something work with UTF-8, so apps could switch one-by-one (this may not work with hooks but still better than nothing...). Add UTF-8 support to MSVC runtime, so at least fopen can be safe (people have been asking for it forever). Add FILE_FLAG_UTF_8 to CreateFileA. Have Notepad be able to edit UTF-8.

But I suspect the real reason is there was a strong internal opposition to UTF-8 -- maybe it was seen as inferior to UTF-16, maybe it was NIH, maybe they hoped the world will change to follow Windows ways and to put BOM marks in each document...

Oh well, I am glad they have at least changed now.

They couldn't just jump on every technically superior idea, because compatibility is a thing too. And, by the time everyone agreed that utf-8 was preferable, compatibility with their own stuff, which is always especially painful.

It's not as if they were the only ones. I had a lot of utf-related pain in the Linux terminal back in the day.

Vi and Emacs took a long time to handle variable length encodings well. My old Unix editor of choice, NEdit, never managed the switch at all.

I got a mail from my boss in utf-7 once. God knows how that happened.