[weetii]

Hey, yeah, I wrote the article. This (of course) would be more practical. Thanks for pointing it out. I wanted the payload to "live" in actual pixel data rather than hidden text inside an XML file. That’s why I went this way :)

[peter-m80]

The ico file format allows multiple resolution icons, so a lot of data

[weetii]

Good point, I might add a section in the article where I list alternative approaches. Thanks

[dodslaser]

Or just put the entire website in a <foreignObject> and render it in the favicon.

[econ]

You can use any image format. Try using an animated gif.

I don't know what this is but it's huge.

https://news.ycombinator.com/favicon.ico

[cogman10]

If you wanted to play around and do something a little more challenging (though you'd be bulking up the javascript) then one thing you could do is play with a bespoke html compression. You could store the tags in 4 bits `0001` first bit, tag open or close, and the remaining 3 bits indicate which tag is being used (div/p/b/h1/etc). With at least one of the values like `0111` indicating text is following and another tag like `1111` indicating that an unsupported tag follows.

If you extend it out to 8 bits you can pretty nearly store all the html tags (it'd give you 256 tags to play with).