'Kay, I don't know if this comes anywhere close to what the OP wants, but this sort of live browser tab manipulation is possible to do using a mix of a a canvas

'Kay, I don't know if this comes anywhere close to what the OP wants, but this sort of live browser tab manipulation is possible to do using a mix of a a canvas element and the browser's Screen Capture API[1] (plus my JS canvas library, once I merge and publish the required changes into its next release[2]). This solution[3] shows the modified browser tab in a separate browser tab. I've got no idea whether it's possible to do the same sort of trick in the same tab (but probably not). I also have no idea how secure the Screen Capture API is - I'd get very nervous about doing this sort of thing when looking at my bank's online portal! [1] https://developer.mozilla.org/en-US/docs/Web/API/Screen_Capture_API/Using_Screen_Capture https://developer.mozilla.org/en-US/docs/Web/API/Screen_Capt... [2] https://github.com/KaliedaRik/Scrawl-canvas/pull/57 https://github.com/KaliedaRik/Scrawl-canvas/pull/57 [3] Youtube video of the effect: https://www.youtube.com/watch?v=hCi6LmKMAo0 https://www.youtube.com/watch?v=hCi6LmKMAo0