Quick summary: BMP (Bitmap) is a simple raster image format historically used in Windows for raw pixel storage and minimal metadata. PNG (Portable Network Graphics) is a modern lossless compressed format with support for transparency and extensive web-friendly features. This article explains technical differences, practical use-cases, conversion tips, and SEO/web recommendations.
What is BMP?
BMP stands for Bitmap. It is one of the oldest raster image formats and was popularized by Microsoft Windows. A BMP file stores pixel data in a fairly straightforward way — a header describing the image followed by raw pixel values (often padded for row alignment). Historically BMP files were uncompressed, which makes them large but simple to read and write.
Key characteristics of BMP:
- Typically uncompressed (though some BMP variants support RLE compression), resulting in large file sizes.
- Supports a range of bit depths: 1-bit (monochrome), 4-bit, 8-bit (palette), 16-bit, 24-bit (true color), and 32-bit (true color + optional alpha in later versions).
- Simple structure and wide compatibility on Windows platforms and many basic image viewers.
- Limited metadata capabilities compared to modern formats (no standardized EXIF/XMP like JPEG/PNG).
- Rarely used on the modern web because of large file size and limited features for web delivery.
What is PNG?
PNG (Portable Network Graphics) was developed in the 1990s as a patent-free replacement for GIF. PNG uses lossless compression (DEFLATE) and supports features that make it ideal for web graphics and user-interface imagery.
Key characteristics of PNG:
- Lossless compression — reduces file size while preserving pixel-perfect quality.
- Supports truecolor (24-bit) and an alpha channel (RGBA / 32-bit) for full transparency.
- Supports indexed color (palette) for smaller files when colors are limited (PNG-8) and truecolor (PNG-24/32) for photos or detailed images.
- Supports interlacing (Adam7) for progressive display during download.
- Includes metadata support (text chunks, tEXt/iTXt/zTXt) and color management (gAMA, cHRM, sRGB).
- Widely supported in browsers and a standard choice for logos, icons, screenshots, and images requiring transparency.
Technical comparison
| Feature | BMP | PNG |
|---|---|---|
| Compression | Typically none (large files); RLE optional in some variants | Lossless DEFLATE compression (smaller files) |
| Transparency | Limited; native alpha available only in newer BMP variants and not widely supported | Full alpha channel (RGBA) supported |
| Best for | Raw pixel storage, simple Windows graphics, legacy applications | Web graphics, icons, screenshots, images needing transparency |
| Metadata | Minimal (header fields) | Text chunks, color profiles, metadata (better support) |
| Browser support | Poor/limited for web use | Excellent |
| File size | Large for same image | Smaller due to compression |
When to use BMP vs PNG
BMP — when it still makes sense
- Legacy systems or older Windows-based applications that expect BMP files.
- Very simple scenarios where file size is not important and you need a quick, easy-to-write raw bitmap format.
- When you require exact, unmodified pixel dumps for low-level processing or testing.
PNG — the modern choice
- Website assets: logos, icons, interface elements, and images that require transparency.
- Images where lossless quality matters — diagrams, screenshots, and graphics with text.
- Any scenario where you want smaller files, metadata, and wide cross-platform/browser support.
Converting BMP and PNG
Converting between BMP and PNG is straightforward — PNG will typically reduce file size due to lossless compression. Converting PNG to BMP will usually increase file size and remove PNG-specific features like interlacing or textual metadata chunks.
FAQ
- Is BMP better than PNG?
- No — not for modern web or most use-cases. PNG provides compression, transparency, metadata, and browser support. BMP is primarily a legacy, uncompressed bitmap format.
- Can BMP store transparency?
- Some newer BMP variants can store an alpha channel, but support is inconsistent. PNG is the standard for transparency on the web.
- Will converting BMP to PNG reduce file size?
- Usually yes. PNG compression often produces much smaller files than uncompressed BMP for the same image.
- Which format should I use for screenshots?
- PNG — it preserves crisp text and UI elements without artifacts.
Conclusion
BMP and PNG both store raster images, but they serve different eras and needs. BMP is a basic, often uncompressed bitmap format used historically on Windows. PNG is a modern, web-friendly, lossless compressed format that supports transparency, metadata, and optimization for delivery.
For almost all web and design tasks today, choose PNG (or even more efficient modern formats like WebP/AVIF) over BMP. Keep BMP only for specific legacy workflows or very low-level pixel dumps where uncompressed storage is required.