BMP to AVIF Converter
Convert BMP to AVIF in your browser. BMP files usually come from Windows Paint, legacy Windows programs, embedded displays and some scanners; AVIF is the better fit for maximum compression on modern websites. You get an AVIF encoded with libavif (AV1) compiled to WebAssembly, at the quality you choose. Nothing is uploaded.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
BMP expected · other image formats also work
How to use BMP to AVIF
- 1
Add your BMP files: drop them here, choose them, or paste from the clipboard.
- 2
Set the quality. AVIF quality numbers run lower than JPEG: around 55 to 65 already looks excellent. Encoding is slow on phones.
- 3
Click Convert. Each file is decoded and encoded in a background thread on this device.
- 4
Download the .avif files one at a time or together as a ZIP.
Why use Aback Images for bmp to avif
Where the AVIF goes next
AVIF opens in Chrome, Edge, Firefox, Safari 16 and later, Windows 11 Photos, macOS Preview and recent editors.
AVIF next to BMP
A lossy AVIF usually comes out far smaller than the BMP, which stores usually none; RLE for some 4 and 8-bit files.
The first lossy pass
The BMP holds 1, 4, 8, 16, 24 or 32 bits per pixel with nothing discarded yet. This conversion is the first lossy encode these pixels see, and hard edges and flat colour show it first.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
BMP vs AVIF
What changes from BMP to AVIF
Encoding: the BMP uses usually none; RLE for some 4 and 8-bit files; AVIF uses lossy or lossless AV1 intra-frame coding, and the download is an AVIF encoded with libavif (AV1) compiled to WebAssembly, at the quality you choose.
Bit depth: 1, 4, 8, 16, 24 or 32 bits per pixel in the BMP; AVIF allows 8, 10 or 12 bits per channel, and the AVIF written here has 8 bits per channel.
Colour: RGB or an indexed palette in the BMP; AVIF supports YUV 4:4:4 or 4:2:0 with BT.709, Display P3 or BT.2020 primaries, HDR curves possible, written here as 8-bit sRGB.
Transparency: the BMP stores it as an optional fourth byte in 32-bit files, which many programs ignore; the AVIF keeps it as an auxiliary AV1 image stored beside the colour image.
Metadata: the BMP can carry nothing beyond the header's resolution fields (and a colour profile in rare V5 headers); AVIF can carry EXIF, XMP and ICC stored as HEIF items, but nothing is copied across.
About BMP
BMP stores raw, uncompressed pixels. Files are huge but trivially simple, which is why some legacy Windows software, embedded displays and printers still ask for it.
A BMP is a 14-byte file header ('BM' and the offset to the pixels), a DIB header (40 bytes, or 108 and 124 bytes in the V4 and V5 versions that add colour masks and alpha), an optional palette, then pixel rows padded to 4 bytes and normally stored bottom-up.
BMP files usually come from Windows Paint, legacy Windows programs, embedded displays and some scanners.
About AVIF
AVIF uses the AV1 video codec for still images. It is the most efficient widely supported format, often half the size of JPEG, with HDR, wide colour and transparency, but encoding is slow.
An AVIF is a HEIF file, the same ISO base media boxes as MP4, with the brand 'avif'. The picture is an AV1 key frame stored as an image item, and its size, colour and pixel layout are item properties.
When converting BMP to AVIF makes sense
AVIF is the better choice for maximum compression on modern websites, while BMP suits legacy software and embedded systems that require it.
AVIF strengths: Often 50% smaller than JPEG; Excellent at low quality settings; Transparency, HDR and 10/12-bit colour. Drawbacks to weigh: Slow to encode, especially on phones; Not supported by some older software; Can smooth away fine texture at low quality.
Limitations
- BMP stores nearly every pixel literally, so almost any compressed target is several times smaller.
- A 32-bit BMP can carry an alpha byte that most programs ignore; if the image suddenly gains transparent areas after converting, that byte was set.
- AVIF encoding is CPU-heavy, so large images and big batches take noticeably longer than JPG or WebP, especially on phones.
- Some older apps and operating systems cannot open AVIF yet; keep a JPG copy if you share the file widely.
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Frequently asked questions
Does converting BMP to AVIF lose quality?
AVIF is lossy, so detail the eye barely notices is discarded to save space.
Is transparency kept in the AVIF?
Yes. BMP stores it as an optional fourth byte in 32-bit files, which many programs ignore, and the AVIF is written with an alpha channel, so transparent areas stay transparent.
What quality should I choose for AVIF?
AVIF quality numbers run lower than JPEG: around 55 to 65 already looks excellent. Lower values give much smaller files with gentle softening. Encoding is CPU-heavy, so large batches take a while on phones.
Which apps open AVIF files?
Chrome, Edge, Firefox, Safari 16 and later, Windows 11 Photos, macOS Preview and recent editors. It opens in Chrome 85+, Edge, Firefox 93+ and Safari 16+.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.