Using URL values for the cursor property

Gecko 1.8 (Firefox 1.5, SeaMonkey 1.0) supports URL values for the CSS cursor property on Windows and Linux. Mac support was added in Gecko 2 (Firefox 4). This allows specifying arbitrary images as mouse cursors — any image format supported by Gecko can be used.

Syntax

The basic (CSS 2.1) syntax for this property is:

cursor:  [<url>,]* keyword

This means that zero or more URLs may be specified (comma-separated), which must be followed by one of the keywords defined in the CSS specification, such as auto or pointer.

For example, the following value would be allowed:

cursor:  url(foo.cur), url(http://www.example.com/bar.gif), auto;

This will first try loading foo.cur. If that file does not exist or is not valid for some other reason, bar.gif is tried, and if that can't be used either, auto will be used.

Support for the CSS 3 syntax for cursor values got added in Gecko 1.8 (Firefox 1.5):

cursor:  [<uri> [<x> <y>]?,]* keyword

It allows specifying the coordinates of the cursor's hotspot, which will be clamped to the boundaries of the cursor image. If none are specified, the coordinates of the hotspot are read from the file itself (for CUR and XBM files) or are set to the top left corner of the image. An example of the CSS3 syntax is:

.foo  {
  cursor:  auto;
  cursor:  url(cursor1.png) 4 12, auto;
}
.bar  {
  cursor:  pointer;
  cursor:  url(cursor2.png) 2 2, pointer;
} 
/* falls back onto 'auto' and 'pointer' in IE, but must be set separately */

The first number is the x-coordinate, and the second number is the y-coordinate. The example will set the hotspot to be the pixel at (4,12) from the top left (0,0).

Limitations

All image formats supported by Gecko can be used. This means that you can use PNG, GIF, JPG, BMP, CUR, etc. images. ANI is not supported. An animated PNG or GIF will not create an animated cursor.

In Gecko (Firefox) the limit of the cursor size is 128×128px. Larger cursor images are ignored. However, you should limit yourself to the size 32×32 for maximum compatibility with operating systems and platforms.

(Due to a bug in Gecko 1.9.2-1.9.2.6, Firefox 3.6-3.6.6 on Windows limits to 32x32px. This is fixed in later versions.)

Translucent cursors are not supported on Windows releases earlier than XP. This is a limitation of the operating system. Transparency works on all platforms.

URL values as cursors are supported in Windows, OS/2, and Linux (when using GTK+ 2.4 or better) releases of Mozilla. Mac OS X  support was added with Gecko 2 (Firefox 4).

Compatibility with other browsers

Microsoft Internet Explorer 6.0 also supports URI values for the cursor property. However:

• IE only supports CUR and ANI as formats.
• IE doesn't support the CSS 3 syntax with x- and y-coordinates. The cursor image, and the rest of the property, are ignored.