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posted by martyb on Sunday February 23 2020, @10:30AM   Printer-friendly

Helsinki-based software developer, Henri Sivonen, has written a pair of blog posts about UTF-8; why it should be used and how to inform the user agent when it is used.

The first blog post explains problems that can arise when UTF-8 is used without explicitly stating so. Here is a short selection from Why Supporting Unlabeled UTF-8 in HTML on the Web Would Be Problematic:

UTF-8 has won. Yet, Web authors have to opt in to having browsers treat HTML as UTF-8 instead of the browsers Just Doing the Right Thing by default. Why?

I'm writing this down in comprehensive form, because otherwise I will keep rewriting unsatisfactory partial explanations repeatedly as bug comments again and again. For more on how to label, see another writeup.

Legacy Content Won't Be Opting Out

First of all, there is the "Support Existing Content" design principle. Browsers can't just default to UTF-8 and have HTML documents encoded in legacy encodings opt out of UTF-8, because there is unlabeled legacy content, and we can't realistically expect the legacy content to be actively maintained to add opt-outs now. If we are to keep supporting such legacy content, the assumption we have to start with is that unlabeled content could be in a legacy encoding.

In this regard, <meta charset=utf-8> is just like <!DOCTYPE html> and <meta name="viewport" content="width=device-width, initial-scale=1">. Everyone wants newly-authored content to use UTF-8, the No-Quirks Mode (better known as the Standards Mode), and to work well on small screens. Yet, every single newly-authored HTML document has to explicitly opt in to all three, since it isn't realistic to get all legacy pages to opt out.

The second blog post explains how one explicitly communicates to the user agent that UTF-8 is employed in the current document. Always Use UTF-8 & Always Label Your HTML Saying So:

To avoid having to deal with escapes (other than for , &, and "), to avoid data loss in form submission, to avoid XSS when serving user-provided content, and to comply with the HTML Standard, always encode your HTML as UTF-8. Furthermore, in order to let browsers know that the document is UTF-8-encoded, always label it as such. To label your document, you need to do at least one of the following:

  • Put as the first thing after the start tag (i.e. as the first child of head).

    The meta tag, including its ending > character needs to be within the first 1024 bytes of the file. Putting it right after is the easiest way to get this right. Do not put comments before .

  • Configure your server to send the header Content-Type: text/html; charset=utf-8 on the HTTP layer.

  • Start the document with the UTF-8 BOM, i.e. the bytes 0xEF, 0xBB, and 0xBF.

Doing more than one of these is OK.

NB: SoylentNews announced UTF-8 support on 2014-08-18: Site Update: Slashcode 14.08 - Now With UTF-8 Support (And Other News), just 6 months after the site was launched! One of our developers volunteered to do the implementation for them (the code for this site is a fork of the code that underlies slashdot). The offer was declined. A quick check before posting this story still fails to show Unicode/UTF-8 support.

Earlier on SN:
Validating UTF-8 Strings Using As Little As 0.7 Cycles Per Byte (2018)
Announcing UTF-8 Support on SoylentNews (2014)


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  • (Score: 2) by Mojibake Tengu on Sunday February 23 2020, @08:57PM (1 child)

    by Mojibake Tengu (8598) Subscriber Badge on Sunday February 23 2020, @08:57PM (#961548) Journal

    <meta name="viewport" content="width=device-width, initial-scale=1">

    I consider forcing scale on user a very bad practice, ask owners of 4K or 8K displays about it. Or, users of Retina devices.

    There's a good reason why I need to have a scale 2 default on all commodity browsers on my BSD desktop.
    Those web authors forcing scale 1 are shooting themselves in the foot, in a long term their webs will be unreadable for everyone.
    It's the same stupidity as seen on legacy GTK and Qt apps.
    At least Qt can workaround that, it's QT_SCALE_FACTOR=8 for me for common apps, on a 4K.

    --
    The edge of 太玄 cannot be defined, for it is beyond every aspect of design
    Starting Score:    1  point
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    Total Score:   2  
  • (Score: 2) by isj on Sunday February 23 2020, @09:43PM

    by isj (5249) on Sunday February 23 2020, @09:43PM (#961575) Homepage

    The meta viewport is a kludge. It is used as a signal to mobile devices that they don't have to pretend they are a 640x480 pixel device, and instead can show the webpage in a readable manner. Unfortunately without the initial-scale=1 it doesn't work. I grudgingly added it to my website so it looks pretty on mobile devices. I would have preferred a simpler meta tag "yes-you-can-scale-and-reshape-to-fit" but instead we got the viewport tag.

    I don't know anything I can do to make it better for you.