Avoid loose glitter for crafts, cosmetics and parties, and choose glitter-free or certified plant-cellulose alternatives if you must. Check craft supplies for schools and nurseries.
The UK banned microbeads in rinse-off cosmetics in 2018. Glitter is PET film cut into microplastic, so every gram used is a gram released. Quantities are small, a few grams a year per person, but it goes straight to drains and soil.
The catch: biodegradable glitter is often cellulose with a thin aluminium and plastic coating and has not been shown to break down in real freshwater; the safer choice is none.