CUR Format Guide

Available Conversions

About CUR Format

CUR (Windows Cursor) is a raster image format developed by Microsoft for storing custom mouse pointer graphics in the Windows operating system. Introduced with Windows 3.0 in 1990, the CUR format is structurally identical to the ICO (Windows Icon) format, with one critical difference: the CUR file header uses a type value of 2 (instead of 1 for ICO) and includes hotspot coordinate data that defines the precise pixel location where mouse clicks are registered. The format is based on the same ICO container structure, storing one or more cursor images at different sizes and color depths within a single file. CUR files support standard cursor dimensions including 16x16, 32x32, and 48x48 pixels, with 32-bit RGBA color depth that enables full alpha channel transparency for smooth, anti-aliased cursor edges. Each image entry in a CUR file contains an XOR mask for the cursor image and an AND mask for transparency, though modern 32-bit cursors use the alpha channel for transparency instead of the mask-based approach.

History of CUR

The CUR format traces its origins to the earliest graphical versions of Microsoft Windows. When Windows 3.0 launched in 1990, it introduced a graphical user interface that required customizable mouse pointers beyond the basic arrow. Microsoft designed the CUR format as an extension of the existing ICO format, adding hotspot coordinates to enable precise click positioning. Early CUR files were limited to monochrome or 16-color cursors at 32x32 pixels. Windows 95 and Windows NT expanded support to 256-color cursors, and Windows XP introduced full 32-bit RGBA cursors with smooth alpha blending. The introduction of the ANI (Animated Cursor) format in Windows NT 3.5 extended cursor capabilities to include animation sequences based on multiple CUR frames. Despite the evolution of display technology and cursor rendering, the CUR format has remained fundamentally unchanged since its creation, maintaining backward compatibility across all Windows versions. The format remains the native static cursor format for Windows, though modern cursor themes increasingly use higher resolutions to accommodate high-DPI displays.

Key Features and Uses

The CUR format's defining feature is its hotspot data — two 16-bit values specifying the X and Y coordinates of the pixel where the cursor's "active point" is located. For example, an arrow cursor's hotspot is at its tip, while a crosshair cursor's hotspot is at its center. This hotspot information is essential for accurate mouse interaction and is unique to the CUR format among common image formats. CUR files can contain multiple image sizes within a single file, allowing Windows to select the appropriate resolution based on the current DPI setting. The format supports 1-bit, 4-bit, 8-bit, and 32-bit color depths, with modern cursors typically using 32-bit RGBA for full-color graphics with smooth transparency gradients. When converting CUR files to other image formats, the hotspot data is lost since no other common image format supports this metadata. However, the visual cursor image converts cleanly to formats like PNG, ICO, and BMP.

Common Applications

CUR files are primarily used for Windows desktop customization, where users and designers create custom mouse pointer themes. Web designers occasionally reference CUR files in CSS using the cursor: url() property to display custom cursors on web pages, though browser support varies. Software developers embed CUR files as resources in Windows applications to provide context-specific cursors — such as a hand cursor for clickable elements, a resize cursor for window borders, or a crosshair for precision selection tools. Accessibility applications use large or high-contrast CUR files to assist users with visual impairments. Game developers sometimes use CUR files for in-game cursors in windowed mode, though most games implement their own cursor rendering. Cursor theme packs distributed online typically consist of collections of CUR and ANI files that replace the standard Windows system cursors.

Advantages and Disadvantages