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AVIF to BMP converter

Convert AVIF images to BMP format

No watermarkFree & unlimited
All processing happens in your browser. No data is sent to any server.

This is the widest gap in the matrix, from the most efficient still-image codec in common use to a format that applies no compression whatsoever. The result is predictable: files grow by a factor of twenty or more, and nothing about the picture improves, because the AVIF artefacts are copied faithfully into every raw pixel. The one good reason to do it is that a specific piece of legacy Windows software accepts .bmp and nothing else. Alpha is discarded, and transparent regions come out black.

Key facts about AVIF to BMP converter

Key facts about AVIF to BMP converter
Size explosionA 120 KB full HD AVIF becomes exactly 6,220,854 bytes as a 24-bit bitmap, roughly fifty times larger, because the format stores three raw bytes per pixel.
Size formula54 header bytes plus the height times the row width rounded up to a multiple of four. The content of the picture makes no difference to the total.
Alpha discarded to blackThe writer keeps only blue, green and red, so a transparent AVIF loses its alpha and those pixels land as solid black rather than white.
QualityNothing further is lost and nothing gained. Every value the AV1 decoder produced is written exactly, artefacts from the original encode included.
Bitmap variantA 14-byte file header plus a 40-byte info header, 24 bits per pixel, compression field zero, rows stored bottom-up in BGR order.
Decoding requirementChrome from 85, Firefox from 93, or Safari from 16. Without browser AVIF support the file cannot be read and the page reports a load failure.
Bit depthA 10 or 12-bit AVIF is reduced to 8 bits by the canvas before the bitmap is written, so the extra precision is gone.
Opens the resultWindows Paint and Photos, Visual Studio resource editors, legacy Delphi and Visual Basic tooling, GIMP, Photoshop and ImageMagick.

What happens to your file

All of this runs locally. Your AVIF is handed to an Image element through an object URL so the browser's AV1 still-image decoder can produce pixels, and those pixels are drawn onto a canvas belonging to this tab. The page then reads the canvas back with getImageData and writes the bitmap by hand: fifty-four header bytes through a DataView, then the rows in reverse as blue, green and red triples with padding.

About this tool

  1. 1

    Add the AVIF

    Drop up to twenty .avif files onto the target area, or click to browse. Each may be as large as 500 MB.

  2. 2

    Think about the size first

    A full HD frame produces a six megabyte bitmap. Pick a resize preset if the destination does not need full resolution.

  3. 3

    Flatten transparency beforehand

    If the preview shows checkerboard, composite the image over your intended background; the bitmap will otherwise make those areas black.

  4. 4

    Convert and download

    Press Convert. There is no encoder to run so writing is immediate, and multi-file runs return as converted-bmp-files.zip.

Specs & compatibility
Input and outputTakes .avif only (image/avif) and returns .bmp with the image/bmp type; any other extension is refused before decoding.
Conversion pathAVIF to BMP runs in three steps: an <img> element decodes the AVIF, which the browser itself must be new enough to read; the pixels land on a 2D canvas in this tab; then getImageData feeds a 24-bit BI_RGB writer that assembles the file in page memory.
Browser supportThe AVIF side needs Chrome 85, Firefox 93 or Safari 16.4 to decode, while writing the BMP needs nothing from the browser, the bytes being assembled in the page.
Controls for this pairNo quality slider, BMP not being a lossy target here, so the max-dimension presets from 3840 down to 200 px are the only way to hold the BMP down in size against the AVIF.
Batch, caps and namingTwenty AVIF files per run at 500 MB each; one result downloads as a single BMP, several as converted-bmp-files.zip, zipped by JSZip 3.10 in page memory.
Device ceilingThe canvas caps it: past roughly 16,384 px a side Chromium refuses the bitmap and iPhone Safari gives up sooner, so an oversized AVIF fails before any BMP bytes exist.
  • Zip the bitmaps before moving them; raw pixel data usually compresses by eighty percent or more in an archive.
  • The resize presets are your only control over output size, because there is no compression setting to adjust.
  • If the receiving program accepts PNG, choose that instead: equally lossless and orders of magnitude smaller.
  • A very large AVIF may exceed your browser canvas limits before the file size limit, so resize first if a conversion stalls.
  • Browser AV1 decode to raw 24-bit BGR
  • Bottom-up rows with four-byte padding
  • Bitmap header written with DataView locally
  • Twenty files per run, zipped in the tab
  • Supplying an image to a legacy Windows application or installer that loads only bitmap resources.
  • Feeding an embedded display or microcontroller toolchain whose importer reads raw pixel data.
  • Getting a modern web image into a decades-old internal tool.
You removed all compression. AVIF encodes a full HD photograph into around a hundred kilobytes by discarding redundant information and predicting the rest with AV1. A 24-bit bitmap stores three literal bytes per pixel, which for 1920 by 1080 is 6,220,854 bytes regardless of content.
The writer copies only the colour bytes from each canvas pixel and ignores alpha, because a 24-bit bitmap has no alpha channel. A fully transparent canvas pixel reads back as zero everywhere, and zero RGB is black. The JPG path fills the canvas with white first; this one does not.
No. Bitmap storage is lossless, so every value the AV1 decoder produced is written unchanged. What you see are the artefacts the AVIF already had, now stored at enormous expense. A lossless format never repairs earlier lossy compression.
No, the writer always emits 24 bits per pixel with no colour table and no alpha. An 8-bit palette bitmap would be far smaller for graphic content and a 32-bit one would keep transparency, but neither is available. ImageMagick or a desktop editor lets you choose the bit depth.
Your browser cannot decode AVIF. The decoding is done by the browser rather than any code this page ships, so support depends on the version: Chrome 85, Firefox 93 and Safari 16 introduced it. The page reports the failure rather than writing a blank bitmap.

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