ghost-tabs-chrome-extension

To run, make sure serve is installed:

$ npm install -g serve

To run:

$ serve .

It should show multiple .html files and clicking on them should show the various favicon demos.

Notes from my testing:

64px icon is added to be exhaustive, but the browser shouldn’t ever pick it.
Chrome doesn’t ever choose the 16px favicon unless it’s a .ico file. Then, if the window.devicePixelRatio === 1, it uses the 16px variation.
It doesn’t always select the larger icon. If a 64px icon is available, it still picks the 32px icon.
In <link rel="alternate icon" href="foo.bar">, the alternate does nothing.
ICO + PNG, picks ICO at 16px. When adding sizes="16x16" to the ico link, the browser confusingly picks the 32px PNG icon instead.

Resources: