Drop AVIF files. Each is written as PNG with its transparency intact and every decoded pixel kept exactly — at the cost of a much larger file, which the page shows before you save.
What the PNG keeps
PNG is lossless and holds transparency, so a sticker or logo saved as AVIF keeps its transparent background, and the PNG opens in software that refuses AVIF. Every PNG that should be transparent is checked for an alpha channel before it is offered.
The browser decodes AVIF to 8 bits per channel in sRGB, so a 10- or 12-bit AVIF becomes an 8-bit PNG. 16-bit PNG output is not offered, because the extra bits were never decoded.
Questions about AVIF to PNG
Does AVIF to PNG keep transparency?
Yes. PNG holds alpha, and each PNG is checked for it when the AVIF had transparent areas.
Why is the PNG so much larger than the AVIF?
AVIF is one of the most efficient lossy formats; PNG stores every pixel losslessly. Ten times larger is not unusual for a photograph.
What happens to 10-bit colour?
The browser decodes AVIF to 8 bits per channel before anything is written, so the PNG is 8-bit. Keep the AVIF if the extra depth matters.
Are my files uploaded?
Nothing is uploaded: the picture is read, converted and checked in this browser tab.