Quick answer: Unity URP bloom flickering at bright pixels under ACES tonemap? Bloom prefilter operates pre-tonemap - drop the threshold or use a soft knee curve to avoid bright-pixel bouncing.

Sunset scene has fireflies dancing across specular highlights. Disabling ACES kills the flicker.

Lower threshold

Volume > Bloom > Threshold = 0.9. Default 1.0 creates a step that ACES amplifies into shimmer.

Enable soft knee

Soft Knee = 0.5. Smooth ramp instead of binary; flicker disappears.

Or clamp HDR

Camera > HDR > clamp max to 8.0. Limits the input range bloom sees; eliminates pixel bouncing from specular sparkles.

“Bloom prefilter sees raw HDR. Tonemap is downstream. Sparkles live in the gap.”

Use the bloom debug visualization to see the prefilter output directly. If it sparkles there, the bloom output will too.