The CUR file (.cur, .ani)

A CUR file holds a mouse pointer for Windows: the arrow, the hand over a link, the text beam, the busy circle or a custom design. Microsoft's documentation describes cursor files as storing several images at different sizes, like icons, and Windows picks the best match for the screen.

What makes a cursor more than an icon is the hotspot: in Microsoft's words, the pixel that marks the exact screen location affected by a mouse event. For an arrow it's the tip, for a crosshair the centre, for a pencil the point. A cursor with the hotspot in the wrong place clicks a few pixels away from where it seems to point.

• Static cursors use .cur. Each image can be a monochrome bitmap, a colour bitmap, a 32-bit image with an alpha channel, or a PNG.
• Animated cursors use .ani, a different container that holds a sequence of cursor images with timing. The Windows busy and working-in-background pointers are animated cursors.

Cursor files turn up in Windows pointer schemes and cursor packs, inside programs (as resources in .exe and .dll files), and on websites, which can set a custom pointer with CSS.

Because the layouts are so close, an ICO file can be turned into a cursor by changing its type to 2 and writing a hotspot into each directory entry. Going the other way loses the hotspot. An .ani file is a RIFF container, the family WAV and AVI belong to, holding the frames plus chunks that set how long each frame shows and in which order.

Unlike icons, cursor sizes change in steps. Microsoft lists the default cursor size Windows uses at each display scaling level:

The pointer size slider in Settings makes cursors bigger still. A cursor file with a single 32-pixel image works everywhere, but on a high-resolution screen it's scaled up and looks blurry; include the larger sizes for a sharp pointer. The visible shape is usually smaller than the image, with transparent space around it.

1. 1Save the .cur or .ani file somewhere permanent; Windows' own cursors live in C:\Windows\Cursors.
2. 2Open Start > Settings > Bluetooth & devices > Mouse, and under Related settings choose Additional mouse settings.
3. 3In Mouse Properties, open the Pointers tab.
4. 4Under Customize, select the pointer to replace (Normal Select, Text Select, Busy and so on), choose Browse, pick your file and choose Open.
5. 5Optionally choose Save As to keep the set as a scheme, then OK.

Cursor packs often include an .inf file that installs the whole scheme: right-click it and choose Install (on Windows 11, under Show more options), then select the scheme on the Pointers tab. To go back, pick Windows Default in the Scheme list. For size and colour without custom files, use Settings > Accessibility > Mouse pointer and touch.

The CSS cursor property accepts image URLs, and MDN notes that desktop browsers broadly support the .cur format alongside PNG and SVG:

/* .cur first, a PNG with an explicit hotspot as the next choice,
   and a keyword fallback, which is required */
.canvas {
  cursor: url("pencil.cur"), url("pencil.png") 2 30, crosshair;
}

• A keyword fallback is required. Without one (auto, pointer, crosshair…) at the end of the list, the whole declaration is invalid and ignored.
• The hotspot comes from the file. If you don't give x and y after the URL, a .cur file's own hotspot can be used. A PNG has no hotspot, so give one, or the top-left corner is used.
• Size limits: according to MDN, Firefox and Chromium ignore cursor images larger than 128 × 128 pixels, and 32 × 32 is the recommended size.
• No animation: current browsers don't play .ani cursors, and old-style inverting pixels aren't supported either.
• Touch screens have no cursor. On phones the setting has no effect, and on iPadOS only the text value changes the pointer.

• Use a cursor editor. Cursor and icon editors let you draw each size, set the hotspot visually, and save .cur and .ani files. This is the easiest way to get the hotspot right.
• From an ICO, by hand: make a 32 × 32 icon (for example magick input.png -resize 32x32 icon.ico), then in a hex editor change byte 2 from 01 to 02 and write the hotspot's x into bytes 10–11 and y into bytes 12–13, low byte first. Rename it to .cur. Do this for each directory entry if the file has several images.
• Check your tool's output. In our tests, ImageMagick 6 saved a file named .cur with the icon type (1) in its header, so Windows would treat it as an icon. Look at the first four bytes: a cursor starts 00 00 02 00.
• Open or convert one: magick pointer.cur pointer.png writes one PNG per image inside; Python's Pillow opens .cur files too, though it can't write them.
• Inspect one: on Linux and macOS, the file command prints the image count, size and hotspot, for example hotspot @1x1.

• Clicks land in the wrong place. The hotspot is wrong, often (0, 0) from a tool that didn't set one. Fix it in a cursor editor or in bytes 10 to 13 of each directory entry.
• The custom cursor doesn't show on a website. Check the fallback keyword is there, the URL loads (open it directly), and the image is no bigger than 128 × 128.
• The cursor is blurry. It has only one small image, scaled up for a high-DPI screen or a bigger pointer size. Add 48, 64 and larger images.
• Windows won't accept the file. It may be a PNG or ICO renamed to .cur. Check the first bytes: 00 00 02 00 for a cursor.
• Black boxes or odd edges in old software. 32-bit cursors with alpha need a reasonably recent Windows; very old systems expect 1- or 4-bit images with an AND mask.