> [...] rendering to canvas allows programmers to have pixel perfect control over the look of their applications across all devices. Canvas-based fingerprintin

> [...] rendering to canvas allows programmers to have pixel perfect control over the look of their applications across all devices. Canvas-based fingerprinting due to rendering differences is a thing, so using the canvas is not pixel-perfect either. Creating an UI library atop of that is a lot of work, though to be fair certainly manageable by Google. Remember, a UI library is not just about putting things on the screen, but sanely defining layouts, interactions, accessibility... > Specifically, lots of specialized applications have UI components which do not have a corresponding HTML standard I think that is the entire point behind Web Components [0], and if one really really don't want more DOM elements for their visuals, then the CSS Paint API and in fact the whole Houdini initiative [1] should be pursued instead, at least at the Google scale. Besides these technical points, interoperability should be considered. Web browsers do a lot of work to match user expectations in behaviour to their native operating systems, as well as web conventions. (The classic example infractions being: links that cannot be control-clicked or middle-clicked to open on new tabs because they are not actual links but elements with click handlers; or not being able to scroll with page up/down, arrows, or middle-click, because the page reimplements scrolling in an unsemantic way) Making your own UI toolkit is bound to all those problems, and those are user-facing problems that will affect the often-ignored long tail of users with unconventional setups. Look at Flutter for Web, for example [2], it definitely feels entirely different from a regular website, even if it were to look the same. The scrolling does not respect my system settings, interaction is limited to only the most-common method, image scaling is subtly different. And as Google observed themselves, extensibility and the user-agent should be considered before making such a decision, but it appears they consider it a liability in detriment of the user. [0]: https://developer.mozilla.org/en-US/docs/Web/Web_Components https://developer.mozilla.org/en-US/docs/Web/Web_Components [1]: https://developer.mozilla.org/en-US/docs/Web/Houdini https://developer.mozilla.org/en-US/docs/Web/Houdini [2]: https://gallery.flutter.dev/ https://gallery.flutter.dev/