BMP vs ICNS
A detailed comparison of BMP Image and Apple Icon Image — file size, quality, compatibility, and which format to choose for your workflow.
BMP Image
Raster & Vector ImagesBMP is an uncompressed raster image format native to Windows. Files are large but preserve exact pixel data with no compression artifacts. Rarely used on the web due to file size.
About BMP filesApple Icon Image
Raster & Vector ImagesICNS is the icon file format used in macOS applications, containing multiple icon sizes in a single file.
About ICNS filesStrengths Comparison
BMP Strengths
- Dead-simple format — trivially easy to read and write.
- Lossless and uncompressed — perfect bit-exact pixel storage.
- Universally supported in Windows applications since 1985.
- Supports 1, 4, 8, 16, 24, and 32-bit color depths.
ICNS Strengths
- Multi-resolution in one file — OS picks the right size automatically.
- Full alpha transparency.
- Retina @2x variants built in.
- Native macOS support since Mac OS X 10.0.
Limitations
BMP Limitations
- Enormous file sizes — no meaningful compression in typical use.
- Not a web format — browsers support it but nobody serves BMPs over HTTP.
- No metadata support (no EXIF, no ICC profile in practice).
- Multiple header versions mean "a BMP" is ambiguous — parsers must handle several variants.
ICNS Limitations
- macOS-only — Windows and Linux do not use ICNS.
- Few third-party editors create ICNS directly; most designers export PNGs and run iconutil.
- No compression beyond per-size PNG/JPEG2000 encoding.
- Format is effectively frozen — Apple has not expanded it in years.
Technical Specifications
| Specification | BMP | ICNS |
|---|---|---|
| MIME type | image/bmp | image/icns |
| Extensions | .bmp, .dib | — |
| Compression | None (typical); RLE 4/8 bit (rare) | — |
| Color depths | 1, 4, 8, 16, 24, 32 bits per pixel | — |
| Byte order | Little-endian | — |
| Extension | — | .icns |
| Structure | — | Chunked, 4-character chunk IDs |
| Native to | — | macOS |
| Typical sizes included | — | 16, 32, 48, 128, 256, 512, 1024 px + @2x |
Typical File Sizes
BMP
- Small icon (32×32) 4 KB
- Screenshot (1920×1080) ~6 MB
- 4K image (3840×2160) ~25 MB
- Scanned A4 at 300 dpi ~25 MB
ICNS
- Minimal app icon set 20-100 KB
- Full app icon (all sizes, @1x + @2x) 200-500 KB
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Frequently Asked Questions
BMP (Bitmap) is a raster image format developed by Microsoft for Windows. It stores images with no compression by default, resulting in large file sizes but pixel-perfect quality. It has been part of Windows since version 1.0.
BMP (Bitmap) is a raster image formato developed by Microsoft para Windows. It stores images com no compressão by default, resulting in large tamanho do arquivos mas pixel-perfect quality. It has been part of Windows since version 1.0.
BMP files open in Windows Paint, Photos, macOS Preview, GIMP, Photoshop, and virtually any image viewer. All Windows applications support BMP natively.
BMP arquivos abrir in Windows Paint, Photos, macOS Preview, GIMP, Photoshop, e virtually any image viewer. All Windows aplicativos support BMP natively.
PNG is better than BMP in almost every scenario since it provides lossless compression (smaller files), transparency support, and wider cross-platform use. BMP is mainly relevant for legacy Windows applications.
PNG is melhor que BMP in almost every scenario since it fornece sem perdas compressão (smaller files), transparência support, e wider cross-platform use. BMP is mainly relevant para legacy Windows aplicativos.