What is CUR? Windows Cursor File Format Explained
The Microsoft Windows file format for static mouse pointers, storing images plus a click hotspot.
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What is CUR?
CUR is the Microsoft Windows file format used to store static (non-animated) mouse cursors. It is almost identical to the Windows ICO icon format, sharing the same directory-based container structure for holding one or more images.
The key difference from ICO is in the header: CUR files begin with the bytes 00 00 02 00 and each directory entry records a hotspot, the x,y pixel offset that defines exactly where the cursor points. A single CUR file can hold multiple images at different sizes and color depths, letting Windows pick the most suitable one for the display settings; image data may be stored as BMP-style pixel arrays or, in later Windows versions, as embedded PNG data.
How CUR Files Work
A CUR file uses the same directory-based container as Windows ICO. After a 6-byte header, a directory lists each contained image with its width, height, color count, and the byte offset to its data.[1] The distinguishing feature is that the two reserved fields of each ICO directory entry are repurposed in CUR to store the cursor hotspot, the x,y pixel coordinate that marks the exact point the cursor activates.[2] Image data may be a BMP-style pixel array with an AND mask for transparency, or, in later Windows versions, embedded PNG.[1]
CUR vs ICO and ANI
CUR and ICO are byte-compatible apart from the type field in the header (00 00 01 00 for ICO versus 00 00 02 00 for CUR) and the hotspot data.[2] CUR stores only static cursors; animated Windows cursors use the separate RIFF-based ANI format. Because a single CUR can bundle several sizes and color depths, Windows selects the best match for the current display scaling.[4]
Web Use
The format also appears on the web: the CSS cursor property accepts a URL pointing to a .cur file (or other image) to set a custom pointer, with optional fallback coordinates supplying the hotspot.[3]
MKV Technical Specifications
CUR vs Other Image Formats
| Feature | CUR | ICO | PNG |
|---|---|---|---|
| Type | Raster | Raster | Raster |
| Transparency | Yes[4] | Yes | Yes |
| Multiple sizes | Yes[1] | Yes | No |
| Hotspot | Yes[2] | No | No |
| Best for | Mouse cursors[3] | App/site icons | General images |
| Browser support | CSS cursor only | Favicons | Universal |
CUR is structurally almost identical to ICO but adds a cursor hotspot, making it suited to pointer graphics rather than general image display.
Advantages & Disadvantages
Advantages
CUR is the native static cursor format, recognized directly by the Windows operating system and pointer settings.
Like ICO, a single CUR file can bundle several image sizes and color depths so the system can choose the best match.
The header's hotspot field precisely specifies where on the cursor image the pointer actually clicks.
Support for embedded PNG data allows smoothly anti-aliased, alpha-blended cursors on Windows Vista and later.
Disadvantages
CUR cannot store animation; animated Windows cursors use the separate ANI format.
The format is tied to the Windows pointer system and is not a general-purpose interchange image format.
Legacy BMP-style cursor images are uncompressed, which is acceptable only because cursors are very small.
Common Use Cases
CUR exists specifically to define how the mouse pointer looks in Windows.
Custom mouse pointers | FileFormer
Users and theme designers replace the default Windows pointer with custom .cur files.
Application cursors | FileFormer
Software supplies CUR files for context-specific pointers such as crosshairs or resize handles.
Web cursors | FileFormer
The CSS cursor property can reference .cur files to set a custom pointer over web page elements.
Convert CUR Files Free
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Try Image Converter FreeFrequently Asked Questions
What is the difference between CUR and ICO?
They share nearly the same structure, but CUR uses a different identifier in its header (00 00 02 00) and adds a hotspot coordinate per image that defines the cursor's active click point. ICO files store icons and have no hotspot.
Can CUR files be animated?
No. CUR stores only static cursors. Animated cursors in Windows use the separate ANI file format.
Can I use a CUR file on a website?
Yes. The CSS cursor property can point to a .cur file, and Windows browsers will display it as the pointer over the targeted element.
Does CUR support transparency?
Yes. Legacy cursors use a mask for 1-bit transparency, and modern Windows supports embedded PNG data for full alpha-blended, anti-aliased cursors.
How do I make a CUR file?
Dedicated cursor editors or icon tools can create CUR files, letting you draw the image and set the hotspot position.