ICO to BMP Converter
Convert ICO to BMP in your browser. ICO files usually come from website favicons, Windows programs and installers; BMP is the better fit for legacy software and embedded systems that require it. You get an uncompressed 24-bit BMP, or 32-bit with alpha when the image has transparency. Nothing is uploaded.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
ICO expected · other image formats also work
How to use ICO to BMP
- 1
Add your ICO files: drop them here, choose them, or paste from the clipboard.
- 2
There is nothing to tune: the BMP is written uncompressed. Resizing and rotating are under More options if you need them.
- 3
Click Convert. Each file is decoded and encoded in a background thread on this device.
- 4
Download the .bmp files one at a time or together as a ZIP.
Why use Aback Images for ico to bmp
Where the BMP goes next
BMP opens in every operating system and browser.
BMP next to ICO
The BMP is written uncompressed, so expect it to be several times larger than the ICO, which stores each size stored as a headerless BMP or as a complete PNG.
Written without a lossy pass
The BMP is written uncompressed, so the pixels decoded from the ICO arrive unchanged.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
ICO vs BMP
What changes from ICO to BMP
Encoding: the ICO uses each size stored as a headerless BMP or as a complete PNG; BMP uses usually none; RLE for some 4 and 8-bit files, and the download is an uncompressed 24-bit BMP, or 32-bit with alpha when the image has transparency.
Bit depth: 1 to 32 bits per pixel, set per size in the ICO; BMP allows 1, 4, 8, 16, 24 or 32 bits per pixel, and the BMP written here has 24 or 32 bits per pixel.
Colour: RGB or a palette, per image in the ICO; BMP supports RGB or an indexed palette, written here as 8-bit sRGB.
Transparency: the ICO stores it as 8-bit alpha in 32-bit and PNG entries, or a 1-bit mask in old icons; the BMP keeps it as an optional fourth byte in 32-bit files, which many programs ignore.
Other images: the ICO can hold several sizes of the same picture, typically 16, 32, 48 and 256 px; only the main image is converted.
Metadata: the ICO can carry only a directory of the sizes inside, with no EXIF; BMP can carry nothing beyond the header's resolution fields (and a colour profile in rare V5 headers), but nothing is copied across.
About ICO
ICO is a container that bundles several sizes of the same icon (16, 32, 48, 256 px) into one file. It is still the most compatible format for website favicons and Windows app icons.
An ICO starts with a 6-byte ICONDIR (type 1 for icons) and a 16-byte entry per image giving width, height, colour count and offset. Each image is either a BMP without its file header plus an AND mask, or a complete PNG.
ICO files usually come from website favicons, Windows programs and installers.
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.
When converting ICO to BMP makes sense
BMP is the better choice for legacy software and embedded systems that require it, while ICO suits favicons and Windows icons.
BMP strengths: No compression artifacts; Read by very old and very simple software. Drawbacks to weigh: Enormous files; Poor support for transparency; No metadata.
Limitations
- The largest image in the icon is the one converted; smaller sizes that were hand-tuned for 16 px are not carried over.
- A BMP is uncompressed, about 3 bytes per pixel, or 4 with transparency, so expect a large file.
- Some older programs ignore the alpha channel of a 32-bit BMP and show transparent areas as black or white.
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Frequently asked questions
Does converting ICO to BMP lose quality?
BMP is written uncompressed, so the pixels are stored exactly as decoded. Not carried over: any several sizes of the same picture.
Is transparency kept in the BMP?
Yes. ICO stores it as 8-bit alpha in 32-bit and PNG entries, or a 1-bit mask in old icons, and the BMP is written with an alpha channel, so transparent areas stay transparent.
Which apps open BMP files?
Every operating system and browser.
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.