I’m really not sure what you’re trying to say here.
Firefox parses the doctyp from the document. Of course it does. That’s why it’s there. That’s what everything does. What else would it do?
Your footnote is incorrect: `data:text/html,<!doctype html>…` will show a doctype in the dev tools and view source, `data:text/html,…` will not show a doctype in either place, and report the document to be in Quirks Mode. If you want more fun, try `data:application/xhtml+xml,<!DOCTYPE html SYSTEM "about:legacy-compat"><b xmlns="http://www.w3.org/1999/xhtml">Look at this!</b>`.
The history of the doctype is not particularly important any more, and I wouldn’t expect normal developers to know about specific doctypes beyond <!DOCTYPE html>, but its presence is important, and missing it or not knowing it’s necessary for sanity is a definite red flag.
And that’s the first line. Lang, charset, viewport… these are basic essentials that everyone who works in HTML should already know about, even if it’s as simple as “lang="en" means the document is English”, “there must be a <meta charset="utf-8"> right at the top, I dunno why, but it’s necessary like the doctype” and “this viewport tag is to tell mobile browsers that I know what I’m doing on small screens”. Some of the other things in the ten lines aren’t so important for many areas, but you should still be aware of most of them.
The starting point for basic competence is not knowing things, but rather knowing where and how to look: and that requires at least basic broad foundations of knowledge. I would have grave concerns about the foundations of any web engineer that didn’t recognise and know the purpose of at least most of these lines: the first four lines are basic web page functionality, then there’s OpenGraph which it’s important to know the purpose of and what can be achieved thereby, then three lines of mostly mobile browser chrome tweaks and it’s generally wise to be at least aware of this stuff—you get the idea?
I’ve spent too long suffering because of people that don’t know how to write a <title> tag (and writing user scripts to fix this), often because they’re using the Single Page App style and they don’t know how to get their router to change something in the <head>, and maybe don’t even notice it.
You will have to trust when I say the last time I tested this (not when I wrote the comment) using the data scheme without a doctype tag still disabled quirk mode. Clearly you are very knowledgeable about the browser so I am willing to concede defeat here. :)
edit: I suppose what I'm trying to say is: I wouldn't hold it against an engineer with proven experience if they don't know what quirk mode is, but I would become suspicious of their capabilities if they couldn't imagine any justifications for it after giving them a quick rundown of what it is and how it works.
Firefox parses the doctyp from the document. Of course it does. That’s why it’s there. That’s what everything does. What else would it do?
Your footnote is incorrect: `data:text/html,<!doctype html>…` will show a doctype in the dev tools and view source, `data:text/html,…` will not show a doctype in either place, and report the document to be in Quirks Mode. If you want more fun, try `data:application/xhtml+xml,<!DOCTYPE html SYSTEM "about:legacy-compat"><b xmlns="http://www.w3.org/1999/xhtml">Look at this!</b>`.
The history of the doctype is not particularly important any more, and I wouldn’t expect normal developers to know about specific doctypes beyond <!DOCTYPE html>, but its presence is important, and missing it or not knowing it’s necessary for sanity is a definite red flag.
And that’s the first line. Lang, charset, viewport… these are basic essentials that everyone who works in HTML should already know about, even if it’s as simple as “lang="en" means the document is English”, “there must be a <meta charset="utf-8"> right at the top, I dunno why, but it’s necessary like the doctype” and “this viewport tag is to tell mobile browsers that I know what I’m doing on small screens”. Some of the other things in the ten lines aren’t so important for many areas, but you should still be aware of most of them.
The starting point for basic competence is not knowing things, but rather knowing where and how to look: and that requires at least basic broad foundations of knowledge. I would have grave concerns about the foundations of any web engineer that didn’t recognise and know the purpose of at least most of these lines: the first four lines are basic web page functionality, then there’s OpenGraph which it’s important to know the purpose of and what can be achieved thereby, then three lines of mostly mobile browser chrome tweaks and it’s generally wise to be at least aware of this stuff—you get the idea?
I’ve spent too long suffering because of people that don’t know how to write a <title> tag (and writing user scripts to fix this), often because they’re using the Single Page App style and they don’t know how to get their router to change something in the <head>, and maybe don’t even notice it.