https://habilis.net/fixed-point-html/

Fixed-Point HTML

This page is written in Fixed-Point HTML. When the HTML is parsed and
then re-serialized by a browser, it is identical to the original
source code. In other words, it is a "Fixed Point" in the browser's
parse-serialize functionality. The source is invariant, no matter how
many round-trips it makes through outerHTML, it will always be the
same.

How to test Fixed-Point HTML

Fixed-Point HTML can be checked on the fly in the browser. Simply
compare the page's source code against the serialized document's HTML
(plus doctype). I.e., the following expressions will always be true
for Fixed-Point HTML (before DOM modification):

      await (await fetch(document.location.href)).text()
                               ===
    '<!DOCTYPE html>\n'+document.documentElement.outerHTML

Check Fixed-Point HTML

Press the button to check the page. View source to see the code.

How is Fixed-Point HTML different?

For the most part Fixed-Point HTML is the same as typical text-book
HTML. However the syntax is very regimented. Some highlights:

  * No spacing is allowed between html and head/body elements
  * Reserved Characters must always be escaped with character
    entities (e.g. > is &gt;)
  * All elements must be explicitly closed (no skipping </p>)
  * XML-flavored self-closing elements are banished (use <br> instead
    of <br />)
  * Element Attributes are separated by single spaces and must always
    have a double-quoted value (use <img src="a.jpg" alt=""> instead
    of <img src = 'a.jpg' alt >)

Why write Fixed-Point HTML?

I could claim that Fixed-Point HTML is an aid to writing consistent
and error-free HTML (which it can be), but the real reason to code in
Fixed-Point HTML is simply the satisfaction of knowing that you and
the browser are in total agreement about the HTML.

Related Works

  * This page is a truly naked, brutalist html quine. (HN)