BMP Format Guide

Available Conversions

About BMP Format

BMP (Bitmap Image File or Device Independent Bitmap) is a raster graphics image format developed by Microsoft in 1987 for storing digital images on Windows operating systems. BMP files are typically uncompressed, storing pixel data directly with each pixel's color information preserved exactly as captured or created. This results in large file sizes but ensures perfect image quality with no compression artifacts. The format is simple and straightforward, consisting of a file header, an information header, and the actual pixel data stored as a grid of colored dots (bitmap). BMP supports various color depths from 1-bit monochrome through 4-bit, 8-bit, 16-bit, 24-bit, and 32-bit color, with 24-bit being the most common for photographs. While BMP can technically support compression using run-length encoding (RLE), most BMP files are stored uncompressed for maximum compatibility. The format became ubiquitous in Windows environments, serving as the standard for wallpapers, icons, and other system graphics throughout the 1990s and 2000s.

History of BMP

The BMP format was created by Microsoft and introduced in 1987 as part of the original Windows 1.0 and 2.0 operating systems, though it became prominent with Windows 3.0 in 1990. The format was designed to be "device independent," meaning BMP files could be displayed correctly on different types of display hardware without modification—an important feature in an era when monitors varied widely in capabilities. BMP was initially developed to work with OS/2 alongside Microsoft's collaboration with IBM, which is why early BMP specifications included OS/2 bitmap headers. The format went through several versions, with Windows 3.0 establishing the most common BMP structure still used today. During the 1990s, BMP was the de facto standard for bitmap images in Windows, used extensively for desktop wallpapers (particularly the iconic "Bliss" Windows XP wallpaper), Paint program files, game graphics, and software icons. However, as internet usage grew and file size became critical, BMP's uncompressed nature made it impractical for web use. Compressed formats like GIF, JPEG, and later PNG displaced BMP for most applications. By the 2000s, BMP had largely fallen out of favor except in specific use cases requiring uncompressed images or Windows system graphics. Today, BMP is considered a legacy format, maintained primarily for backward compatibility with older Windows software and for specific applications like embedded systems where simplicity is valued over file size.

Key Features and Uses

BMP files store image data as an uncompressed grid of pixels, with each pixel's color value explicitly defined. The format supports multiple color depths: 1-bit (black and white), 4-bit (16 colors), 8-bit (256 colors), 16-bit (65,536 colors), 24-bit (16.7 million colors), and 32-bit (24-bit color plus 8-bit alpha transparency, though rarely used). The 24-bit format is most common, using three bytes per pixel (one each for red, green, and blue). BMP files can optionally be stored with run-length encoding (RLE) compression for 4-bit and 8-bit images, though this is rarely used due to compatibility concerns. The format's pixel data is traditionally stored "bottom-up" (starting from the bottom-left corner), though top-down storage is also supported. BMP includes basic metadata in the file header, including image dimensions, bit depth, and color palette information for indexed color images. The format's simplicity makes it easy to implement and debug, which is why it remains useful in embedded systems and industrial applications. However, BMP lacks support for layers, transparency (in most implementations), progressive loading, or metadata beyond basic image information, limiting its utility for modern applications.

Common Applications

BMP is primarily found in legacy Windows applications and systems where compatibility with older software is required. Windows still uses BMP for certain system graphics, cursors, and icons, particularly in older applications. Microsoft Paint, the basic image editor included with Windows, traditionally defaulted to BMP format, though modern versions support PNG and JPEG. Some older Windows games and software from the 1990s and early 2000s used BMP for sprites, textures, and background graphics. Industrial and embedded systems sometimes prefer BMP for its simplicity and ease of implementation, particularly in contexts where file size is not a constraint. Screenshot tools and screen capture software occasionally use BMP as an intermediate format to preserve perfect quality before conversion. Certain specialized applications in medical imaging, scientific visualization, and technical documentation use BMP when lossless, uncompressed storage is required and file size is not a concern. The format occasionally appears in software development and testing as a reference format for comparing compression algorithms. However, for virtually all modern applications, BMP has been replaced by more efficient formats: PNG for lossless compression, JPEG for photographs, and WebP for web use. BMP files you encounter today are typically either legacy files from older systems or intermediary files in image processing workflows that will eventually be converted to more practical formats.

Advantages and Disadvantages