MSP Format Guide

Convert from MSP

Convert to MSP

About MSP Format

MSP (Microsoft Paint) is a monochrome bitmap image format created by Microsoft for the original Microsoft Paint application, which was bundled with Windows 1.0 in 1985. The MSP format stores 1-bit black-and-white images, where each pixel is represented by a single bit indicating either foreground (black) or background (white). The format was the native file type for Microsoft Paint through Windows 1.0, 2.0, and the early releases of Windows 3.0, making it one of the earliest consumer-level digital image formats on the PC platform. MSP files use the .msp file extension and begin with a 32-byte header containing the image dimensions, aspect ratio information, and a checksum value that also serves to identify the file version. Two versions of the format exist: version 1 (used in Windows 1.0) stores pixel data with simple Run-Length Encoding (RLE) compression, while version 2 (introduced with Windows 2.0) uses a more sophisticated custom compression scheme. Despite its historical significance as the format that introduced millions of users to digital image creation, MSP was replaced by the BMP format when Microsoft Paint was updated for Windows 3.0 in 1990, which brought color support and a more capable bitmap specification.

History of MSP

The MSP format was introduced alongside Microsoft Windows 1.0 on November 20, 1985, as the native file format for Microsoft Paint (originally called Paintbrush in some releases). At the time, the IBM PC ecosystem had no standardized consumer image format, and MSP was designed to meet the modest graphical requirements of the era: monochrome displays with typical resolutions of 640x350 (EGA) or 640x200 (CGA). Microsoft Paint in Windows 1.0 was a simple drawing program that allowed users to create black-and-white line drawings, fill shapes, and place text using basic tools. The MSP format was purpose-built for this application, providing a compact way to store monochrome images with RLE compression that worked well for the simple, high-contrast graphics that Paint produced. When Windows 2.0 launched in 1987, Microsoft updated the MSP format to version 2 with improved compression, but the format remained strictly monochrome. The arrival of Windows 3.0 in May 1990 marked the end of the MSP era: Microsoft Paint was significantly redesigned with color support (16 and later 256 colors), and the BMP (Windows Bitmap) format replaced MSP as the native file type. From that point forward, MSP became a legacy format, though Windows Paint retained the ability to open MSP files for backward compatibility through several subsequent Windows releases. Today, MSP files are encountered primarily in retro computing collections, archived early digital artwork, and legacy document scanning systems from the late 1980s.

Key Features and Uses

The MSP format's structure is straightforward. The 32-byte header contains a magic number identifying the version (0x6144 0x4D6E for version 1, 0x694C 0x536E for version 2), the image width and height in pixels, the horizontal and vertical aspect ratios (used for proper display scaling on monitors of different resolutions), a printer aspect ratio pair, and a checksum calculated from the header fields. Following the header is the pixel data, which is organized as rows of monochrome bitmap data. In version 1, each row uses simple byte-level RLE compression where alternating run counts and literal bytes encode sequences of repeated or unique pixel patterns. Version 2 employs a more complex scheme with a row-offset table at the beginning of the data section, allowing random access to individual scan lines, followed by per-row compressed data using a flag-byte system that supports both repeated-byte runs and literal-byte sequences. The format is limited to exactly 1 bit per pixel, meaning every pixel is either black or white with no grayscale or dithering information stored in the file itself (though the application could apply dithering before saving). Modern image libraries including Pillow (Python Imaging Library) can read and write MSP files, making conversion to and from modern formats straightforward for archival and preservation purposes.

Common Applications

In its heyday during the late 1980s, the MSP format was used primarily within Microsoft Paint for creating simple black-and-white illustrations, diagrams, clip art, and decorative borders. Business users of early Windows created letterheads, simple logos, and presentation graphics in MSP format, while home users explored digital drawing for the first time. Some early desktop publishing applications and word processors could import MSP files for inline illustrations. Document scanning software from the late 1980s occasionally stored scanned pages in MSP format, particularly for fax-quality monochrome document scans. Today, the primary use cases for MSP conversion center around digital preservation and retro computing: archivists and historians convert MSP files to modern formats like PNG or TIFF to preserve early digital artwork and documents, while retro computing enthusiasts convert modern images to MSP format for use with vintage Windows installations. The monochrome nature of MSP makes it similar to other 1-bit formats like XBM, WBMP, and monochrome TIFF, and conversion between these formats is common in legacy system migration projects.

Advantages and Disadvantages