Why is <META HTTP-EQUIV="Content-Script-Type" ...> mostly unused?

user_416224 0
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Related: What's the point of Content-Script-Type and Content-Style-Type.

I wanted to know what the main reasons are that developers don't use

  • <meta http-equiv="content-script-type" content="text/javascript" /> and
  • <meta http-equiv="content-style-type" content="text/css" />

in their web projects. (Me neither, btw.)

Saving one from having to declare the used type on every instance of <script> and <style>, it does not seem to have any drawbacks. Yet, in fact, I have never seen one of them in the wild. Are there any considerations one has to take when relying on these <meta> tags?

html4 html
9 Answers

To add to the discussion.....

  1. Validators for HTML5 will reject these metatag formats as they are deprecated, as some here mentioned. If you care about strict HTML5 validation then you will have to remove them. Because the browser defaults are close to what older browsers used, you will likely be ok without them. I still use them for older browser support.

  2. HTML5 browsers also use "application/javascript" (not "text/javascript") as the correct script type, which older browsers might not support. Again, I would use the older metatag with "text/javascript" just to be safe.

  3. "http-equiv" is a replacement for what the server sends to the browser. My understanding is the metatags will be overwritten by what the server says. But use them if you are worried about missing server info, though the modern browser defaults would likely be enough. If a server did send "Content-Script-Type" and "Content-Style-Type" then you would not need them.

  4. What if you use these metatags because your "inline" CSS and JavaScript is in a web page that was encoded differently from the HTML5 default of UTF-8? My understanding is JavaScript is always stored as UTF-16, but parsed from UTF-8 encoded pages which is the default for HTML5. Many older HTML files are likely saved as ASCII or UTF-8, as well, but could be something else. Most JavaScript parsers, old and new, navigate all those scenarios and sniffs the right encoding, using your metatags as one of many hints to find out what type and encoding the code uses. Many do this regardless of how you encode your files or pages, or what metatag settings are used. So if you do encode HTML pages or files differently, it might not matter what the metatag says. But it doesn't hurt. Unless you include higher level UNICODE/languages in your CSS or scripts, you don't need to worry about changing the encoding or using metatags to control that.

user_55559380

Being HTTP-EQUIV - this has little to do with being deprecated in HTML5 (because here indeed the defaults are JS and CSS - which also makes the type-attribute unnecessary) - there is still the HTTP protocol: https://www.ietf.org/rfc/rfc4229.txt#2.1.30

so you can from the serverside very well send HTTP headers e.g. from PHP 

<?php
header('Content-Type: text/html; charset=UTF-8');
header('Content-Script-Type: text/javascript');
header('Content-Style-Type: text/css');

or node

res.set('Content-Type', 'text/html; charset=UTF-8');
res.set('Content-Script-Type', 'text/javascript');
res.set('Content-Style-Type', 'text/css');
user_86320150
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