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CUR

Windows Cursor MIME Type Reference

image/x-win-cursor Released 1985 · by Microsoft Corporation

The Windows Cursor (CUR) file format is a proprietary image format developed by Microsoft for mouse pointers. It is structurally identical to the Windows Icon (ICO) format, with two key exceptions: an identification byte in the header marking it as a cursor rather than an icon, and the inclusion of a 'hotspot'—a specific X and Y coordinate within the image grid that defines the exact point where user clicks are registered.

Icons & Cursors Transparency Production Ready

Technical Specifications

MIME Type
image/x-win-cursor
Extensions
.cur
Container
ICO/CUR Container File
Compression
Uncompressed (BMP) & PNG (Supported in newer versions)
Algorithms
None (DIB / BMP)Deflate (If PNG embedded)
Color Depth
1-bit (Monochrome), 4-bit (16 colors), 8-bit (256 colors), 24-bit (True Color), 32-bit (True Color with Alpha)
Metadata
None
Capabilities
Transparency
Animation
Progressive Loading
Alpha Channel
HDR Support
Official Specification
Aliases: image/cursorapplication/x-cursorimage/vnd.microsoft.icon

Magic Bytes & HTTP Headers

File Signature (Magic Bytes)
00 00 02 00
ASCII: \x00\x00\x02\x00
HTTP Headers
Content-Type: image/x-win-cursor
Content-Type: image/cursor
HTML Accept Attribute
accept="image/x-win-cursor, .cur"

Browser Support Matrix

Browser Status Min Version
Chrome Chrome
Supported 1
Firefox Firefox
Supported 1
Safari Safari
Supported 1.2
Edge Edge
Supported 12
Internet Explorer Internet Explorer
Supported Legacy

Advantages & Limitations

Advantages
  • Natively supported by Windows for desktop cursor customization
  • Widely supported by modern web browsers for custom CSS cursors
  • Supports an exact hotspot coordinate, which standard image formats like PNG and JPEG lack
Limitations
  • Legacy format that is being gradually replaced by SVG and PNG for web implementations
  • Does not support animation (animated cursors use the distinct .ani format)
  • The MIME type is highly fragmented across systems (e.g., image/cursor, image/x-win-cursor, application/x-cursor)

Developer Code Snippets

import magic
print(magic.from_file('pointer.cur', mime=True)) # Outputs 'image/x-win-cursor'
const fs = require('fs');
const buffer = Buffer.alloc(4);
const fd = fs.openSync('pointer.cur', 'r');
fs.readSync(fd, buffer, 0, 4, 0);
fs.closeSync(fd);
const isCUR = buffer.toString('hex') === '00000200';
console.log('Is CUR File:', isCUR);
import "net/http"

mimeType := http.DetectContentType(fileBytes)
// Note: Go's standard library may detect this as application/octet-stream
fmt.Println(mimeType)
$mime = mime_content_type('pointer.cur');
echo $mime; // Typically resolves to image/x-win-cursor or application/octet-stream

File Detection Steps

How to programmatically detect a image/x-win-cursor file by reading its raw bytes:

  1. 1 Check the first 4 bytes for the exact hex signature 00 00 02 00.
  2. 2 Parse the image directory at offset 4 to extract the hotspot coordinates at bytes 4 and 6 of the directory entry.

Software Support

M
Microangelo
R
RealWorld Cursor Editor
I
ImageMagick
G
GIMP

Free Online Tools for CUR

CUR Format Comparisons

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Interactive iframe Widget
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JSON API

All data on this page is available as a free, open JSON API. Use it in your project, documentation, or tooling.

GET https://freewebptojpg.com/mime/image/cur.json Open JSON
Free to use
No auth required
CORS enabled
Use from any domain
Cached 24h
Cache-Control headers set

Frequently Asked Questions

What is the magic byte for image/x-win-cursor?

A CUR file always begins with the 4-byte sequence 00 00 02 00 in hexadecimal. The '02' differentiates it from an ICO file, which uses '01'.

Is image/x-win-cursor supported in web browsers?

Yes. Most modern web browsers support .cur files specifically for use within the CSS 'cursor' property (e.g., cursor: url('custom.cur'), auto;).

What is a cursor 'hotspot'?

Unlike a standard image, a cursor must define exactly which pixel triggers a click event. A CUR file stores this precise X and Y coordinate (the hotspot) in its image directory header.

Related Formats

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