11 January, 2023

It all started when I saw no-ht.ml, Terence Eden‘s hilarious response to Salma Alam-Naylor‘s excellent HTML is all you need to make a website. The latter is an argument against both the silly amount of JavaScript with which websites routinely burden their users, but also even against depending on CSS. As a fan of CSS Naked Day and a firm believer in using JS only for progressive enhancement, I’m obviously in favour.

Screenshot showing Terence Eden's no-ht.ml website, which uses plain text ASCII/Unicode art to argue that you don't need HTML. — Obviously no-ht.ml is to be taken as tongue-in-cheek, but as you’re about to see: it caught my interest and got me thinking: how could I go *even further*.

Terence’s site works by delivering a document with a claimed MIME type of text/html, but which contains only the (invalid) “HTML” code <!doctype UNICODE><meta charset="UTF-8"><plaintext> (to work around browsers’ wish to treat the page as HTML). This is followed by a block of UTF-8 plain text making use of spacing and emoji to illustrate and decorate the content. It’s frankly very silly, and I love it.¹

I think it’s possible to go one step further, though, and create a web page with no code whatsoever. That is, one that you can read as if it were a regular web page, but where using View Source or e.g. downloading the page with curl will show you… nothing.

I present: The Page With No Code! (It’ll probably only work if you’re using Firefox, for reasons that will become apparent later.)

Screenshot showing my webpage, "The Page With No Code". Using white text (and some emojis) on a blue gradient background, it describes the same thought process as I describe in this blog post, and invites the reader to "View Source" and see that the page genuinely does appear to have no code. — I’d encourage you to visit *The Page With No Code*, use View Source to confirm for yourself that it truly has no code, and see if you can work out for yourself how it manages this feat… before coming back here for an explanation. Again: probably Firefox-only.

Once you’ve had a look for yourself and had a chance to form an opinion, here’s an explanation of the black magic that makes this atrocity possible:

The page is blank. It’s delivered with Content-Type: text/html. Your browser interprets a completely-blank page as faulty and corrects it to a functionally-blank minimal HTML page: <html><head></head><body></body></html>.
<body> and <html> elements can be styled with CSS; this includes the ability to add content: ::before and ::after each element. If only we could load a stylesheet then content injection is possible.
We use the fourth way to inject CSS – a Link: HTTP header – to deliver a CSS payload (this, unfortunately, only works in Firefox). To further obfuscate what’s happening and remove the need for a round-trip, this is encoded as a data: URI.

Screenshot showing HTTP headers returned from a request to the No Code Webpage. A Link: header is highlighted, it contains a data: URL with a base64-encoded CSS stylesheet. — The stylesheet – and all the page content – is right there in the Link: header if you just care to decode it! Observe that while 5.84kB of data are transferred, the browser rightly states that the page is zero bytes in size.

This is one of the most disgusting things I’ve ever coded, and that’s saying a lot. I’m so proud of myself. You can view the code I used to generate this awful thing on Github.

My server-side implementation of this broke in 2023 after I upgraded Nginx; my new version doesn’t support the super-long Link: header needed to make this hack work, so I’ve updated the page to use the Link: to reference the CSS file rather than embed it via a data URI. It’s not as cool, but it at least means you can still see the page. Thanks to Thomas Bradshaw for pointing out the problem.

Footnotes

¹ My first reaction was “why not just deliver something with Content-Type: text/plain; charset=utf-8 and dispense with the invalid code, but perhaps that’s just me overthinking the non-existent problem.