Earlier quoted context omitted.
I'm pretty sure that's because the entire of the site has an 8px Gaussian blur on it: .site-main[data-astro-cid-bpoqdqeq] { backdrop-filter:blur(8px); } Why, exactly? The page looks visually identical when I disable that rule, but the performance skyrockets. I realize that it's probably vibecoded, but come on.
does it not affect the vignette effect? i can't test it (on the phone) but performance seems fine for me (and i have js jit disabled lol) yes they should have tested the site on firefox, but idk i wouldn't expect css gaussian blur of all things to cause slowdowns in some browsers
Gaussian blurs are extremely performance intensive. They need to be calculated for every individual pixel, and the per-pixel computation involves averaging the colors of dozens or hundreds of adjacent pixels. This site applies it to the entire , which spans the entire screen's width and height on mobile, which means that it has several million pixels. That's fine if the browser only has to calculate it once, but when you're scrolling the browser has to perform those calculations for every single pixel on every single frame.
Apparently Chromium and Safari downscale the sampled texture which makes it less accurate but more performant, but Firefox doesn't do that because it prioritizes accuracy over performance, which explains why it only stutters on Firefox.