AVIF to BMP Converter

AVIF makes very small files, but plenty of software still cannot open it — especially older Windows programs and tools that only accept bitmaps. This converter decodes each AVIF with your browser's built-in decoder and writes a plain BMP: 24-bit colour on a background you choose, 32-bit with the transparency kept, or 8-bit greyscale.

How to use this tool

1. Drop one or more .avif files.
2. Pick the BMP type: 24-bit, 32-bit with transparency or 8-bit greyscale.
3. For 24/8-bit choose the fill colour for transparent areas; optionally set a DPI or a max size.
4. Download the BMPs.

Formula

BMP size = 14 + 40 (108 for 32-bit) [+ 1,024 for the 8-bit palette] + height × row, with row = width × bytes per pixel rounded up to a multiple of 4.

AVIF can carry 10- or 12-bit and HDR colour; the browser maps it to 8-bit sRGB before saving, as BMP holds 8 bits per channel. Decoding needs Chrome 85+, Edge 121+, Firefox 93+ or Safari 16.4+. Animated AVIF files give their first frame.

Example

A 40 × 25 px AVIF saved as a 32-bit BMP is 14 + 108 + 25 × 160 = 4,122 bytes, because each row holds 40 × 4 = 160 bytes. As 24-bit, each row is 120 bytes and the file is 54 + 25 × 120 = 3,054 bytes. A 1920 × 1080 AVIF of 150 KB becomes a 24-bit BMP of 6,220,854 bytes.