I think I assumed 'tracking pixel' was just a metaphor — you mean they're literally serving 1x1 images? Why not 0x0 images? Why not a single transparent pixel?
The pixels are transparent. Gif was the earliest format that supported this.
0x0 pixels arent a valid image, iirc.
All of tracking pixels I've worked with come with a css attribute "hidden", so they don't actually show except in some edge cases.
Huh... I thought browsers didn’t fetch hidden images. Or is that only if the image or its parent elements are "display: none"?
I don't _think_ either case it true.
Because no one thought that the background would change or something like dark-mode would appear ;) 1x1 image was "good enough".
I remember learning ~20 years ago to always set `background-color: #fff` since, in those days of Netscape, a user could easily customise their browser's default background color. It was very useful to have someone on the dev team who was weird enough to have done just that! :)
Well, you still can.. (browser.display.background_color in Firefox)
Sure, but that's why I said "easily" - iirc, it was more an end-user feature than a power-user one.