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What the hell is <!DOCTYPE html>?

Amandeep Singh Malhotra on June 29, 2022

<!DOCTYPE html> > <html lang="en"> <head> <title>Document</title> </...

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Thomas Bnt ☕ • Jun 29 '22

Cool post about DOCTYPE! 👍🏼

Don't hesitate to put colors on your codeblock like this example for have to have a better understanding of your code 😎

console.log('Hello world!');

Amandeep Singh Malhotra • Jun 29 '22

Hey Thomas, since was my first post at dev.to, I was not aware of this. Thanks for your input. :)

Thomas Bnt ☕ • Jun 29 '22

Oh don't worry! Very nice first post! And welcome to DEV! 👋🏼🚀

Albert Sanchez • Jul 6 '22 • Edited

console.log('hi');

Peter Vivo • Jun 29 '22

I take look my old cv (around 2008) doctype and that was:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">

When debugged :

console.dir(document.doctype)

{
  publicId: "-//W3C//DTD HTML 4.0//EN"
  systemId: "http://www.w3.org/TR/REC-html40/strict.dtd"
...restOfDoctype
}

Saddly my old flash animation and program does not run in modern browser, I lost them, just keep the doctype.

Randell Brian Knight • Jun 30 '22

Very nice article about DOCTYPE! 🎉 It's good to have some useful background information about these topics. Thank you, Amandeep 😎

Amandeep Singh Malhotra • Jul 1 '22

Thank you 🙂

Kunal Keshan • Jun 29 '22

Awesome! didn't know about the quirks mode fallback if the DocType is not mentioned.

CraftyMiner1971 • Jul 3 '22

Thanks for the simple explanation of the DocType! I'm so glad that the W3C people simplified the DocType, cos i would not be able to remember all that fancy code that went into the former starting line for HTML files.

Amandeep Singh Malhotra • Jul 6 '22

Thank you for going through this article. I have written another article which explains the this keyword in javascript. If you'd like to explore it, please go through this link. Thanks! ✌️

Kithmini • Jun 30 '22

Interesting Article

🚩 Atul Prajapati 🇮🇳 • Jun 30 '22

In starting days of my learning web development i have asked several times to my institute teacher but they are unable to solve my curiosity 😌 thanks for your priceless effort 🙏🙏 shatsriya a kal 🙏

UponTheSky • Jun 29 '22

Nice Investigation! It was really informative!

Yongchang He • Jun 29 '22

This is interesting!

InvalidLenni • Jul 2 '22

Thanks! I didn't know that, but now I know that! Nice post about <!DOCTYPE>

Wj • Jun 29 '22 • Edited

Too detailed for 1 line of code 🤯. Good practice though especially when it comes to bigger stuff to discuss about.

Andrew Baisden • Jul 1 '22

Nicely done good explanation.

Amandeep Singh Malhotra • Jul 1 '22

Thank you 🙂

imonem • Jul 5 '22

I love history lessons, keep'em comin'

Steven Barrios • Jul 6 '22

This was a great post!

Tomasz Jakut • Jul 7 '22

Older HTML versions weren't actually based on SGML. That was just the theory but it wasn't done in practice. Otherwise it would require browsers to fetch all these .dtd files to parse HTML elements correctly – especially if someone came up with their own one. Parsing rules were more likely just hardcoded into the browsers and later just codified in HTML5 spec.

BTW DTD-based DOCTYPEs created one other issue: DDOS-ing W3C's servers ;)

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