According to Can I Use and MDN Firefox supports filter: url(link#id)
expressions for defining filters.
This minimal working example shows that is not always correct.
Set up the project by:
pnpm install
pnpm run dev
Use for example Chrome to view the website at localhost:5173:
Now try the same with Firefox:
The filters are stored in src/assets and loaded in App.svelte.
This issue was first experienced by Skeleton, which led me to create this minimal working example. See a dedicated discussion here: Why are filters not supported in Firefox?.