ICO to BMP

ICO to BMP is a free tool that converts an ICO icon file into a BMP bitmap entirely in your browser.

Is BMP the right format for your icon?

BMP is a reasonable destination when a desktop program, legacy Windows workflow, or device specifically requires a bitmap file. It stores raster pixels in a straightforward form and is widely recognized by Windows image software.

BMP is usually a poor choice for a website favicon or downloadable web image. ICO is designed to package icon sizes such as 16 by 16, 32 by 32, 48 by 48, and 256 by 256 pixels in one file. BMP normally contains one image, lacks dependable transparency across applications, and is commonly larger.

• Use BMP when a program explicitly requests a .bmp file or an older Windows process expects bitmap data.
• Keep ICO for Windows application icons and favicon workflows that need several resolutions in one file.
• Consider ICO to PNG when you need lossless editing and reliable transparency.
• Consider ICO to JPG only for artwork that does not need transparency and can tolerate lossy compression.

Turning a low-resolution or previously compressed icon into a lossless BMP cannot restore missing detail.

Private browser-side conversion

The conversion happens entirely in your browser, and the ICO file is never uploaded to a server. This matters for private application icons, unreleased branding, and internal interface assets because the input remains on your device.

Decoding ICO entries and creating BMP pixel data still uses your device's memory. A very large or unusually complex ICO may take more resources than a small favicon, and the practical limit depends on the browser and device.

Why can transparency look different after conversion?

Transparency can look different because ICO supports icon-specific transparency masks and alpha channels, while BMP transparency depends on the BMP variant and the application reading it. Some BMP readers understand alpha data, but others treat transparent pixels as black or another solid color.

• ICO is a container that can hold several raster images at different sizes and color depths. Modern ICO files may contain PNG-compressed image data, while older entries often use DIB data related to BMP.
• BMP commonly stores uncompressed pixel data. Some BMP variants support run-length encoding, but BMP is generally chosen for compatibility rather than compact storage.
• Neither format provides ordinary image animation. Multiple images inside an ICO represent icon sizes or pixel formats, not animation frames.
• Browsers commonly recognize ICO for favicons. BMP works in many desktop applications and has broad browser support, but it is often less suitable for web delivery than PNG, WebP, or JPG because BMP files are commonly larger.

File size usually increases when a compressed ICO entry becomes an uncompressed BMP. For illustration, a 256 by 256 image stored as 32-bit uncompressed pixels needs about 262,144 bytes for pixel data alone, plus headers and any row padding. A 32 by 32 image at the same depth needs about 4,096 bytes plus overhead. These calculations are examples rather than predictions because the selected icon entry, output bit depth, and BMP encoding affect the final size.

How should you handle an ICO that contains several sizes?

You should inspect the BMP dimensions after conversion because a BMP conventionally contains a single raster image rather than an ICO-style collection of sizes. This tool does not specify how it handles an ICO file when several embedded entries are present.

A 16 by 16 icon may look sharp at its intended size but blocky when enlarged. A 256 by 256 entry retains more detail for editing, though it also creates a larger uncompressed bitmap. Check the pixel dimensions in an image editor before placing the BMP into another application.

Malformed headers, truncated image data, or a file that merely has an .ico extension may prevent meaningful decoding. An empty file contains no icon image to convert. Spaces, numbers, punctuation, accented letters, and non-Latin characters in the filename do not change the encoded pixels, although the operating system or browser may adjust the saved filename.

Worked conversion scenarios

These examples show what to expect without assuming a particular embedded-image selection rule.

• An ICO contains one opaque 32 by 32 image for a legacy toolbar. The BMP represents the same raster artwork in bitmap form, and it will commonly be larger if stored without compression.
• An ICO contains a 256 by 256 PNG-compressed entry with a soft transparent shadow. The BMP may require substantially more storage, and the shadow's appearance depends on whether the receiving application interprets BMP alpha data.
• An ICO contains 16 by 16, 32 by 32, and 48 by 48 versions of a logo. The tool's handling of the three icon resources is unspecified, so check the dimensions of any resulting BMP before use.
• A blurry 24 by 24 source icon is converted to BMP. The pixels can be stored losslessly in the BMP, but the conversion cannot reconstruct sharper edges or additional detail.

Frequently asked questions

Can I convert an ICO by renaming the file extension?

No. Renaming .ico to .bmp changes only the filename, not the headers or pixel organization inside the file. Software expecting a real BMP may reject the renamed file or report that it is damaged.

Can Microsoft Paint open a BMP made from an icon?

Microsoft Paint supports BMP as a standard Windows image format. If transparency is involved, verify the background after opening because Paint versions and other bitmap readers can interpret alpha data differently.

What happens if the ICO contains only a 16 by 16 image?

The available artwork contains only 256 source pixels, so conversion cannot create a detailed large image. Enlarging the BMP will make individual pixels or interpolation blur more visible.

Does BMP support compression at all?

Some BMP variants support RLE compression for indexed 4-bit or 8-bit images, and embedded compression methods exist in parts of the format family. Many BMP files are uncompressed, so do not assume a converted bitmap will be smaller merely because BMP has optional compression fields.

Should I keep the original ICO after making a BMP?

Yes. The original may contain additional resolutions, transparency information, or compressed entries that a single BMP does not retain as an icon collection. Keep it until you have checked the BMP's dimensions, edges, background, and appearance in the target software.