Drop any mix — WebP, AVIF, GIF, BMP, TIFF, SVG, HEIC where the browser reads it. Each file is written as PNG, which keeps every decoded pixel and any transparency exactly.
What it opens
Everything this browser decodes, plus TIFF on every browser through this site's own TIFF reader (first page; the TIFF to JPG mode lists every page) and SVG drawn at its own size with external references removed. HEIC opens where the browser reads it itself, which Safari does. A file that does not open stays in the list with the reason.
What PNG costs
PNG is lossless: it stops further loss but cannot undo what a lossy source already discarded, and for photographs it is usually several times larger. The byte count of every PNG is shown next to its source. When the source is a photograph, the page says what WebP or JPEG would have cost instead — advice only; the PNG you asked for is what is written.