Icon file format

Writable

image

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Identify it

Extensions	`.ico`
MIME types	`image/vnd.microsoft.iconimage/x-icon`
Signatures	`00000100` at byte 0 (Icon file format)
PRONOM	`x-fmt/418`
Wikidata	`Q729366`
Apple UTI	`com.microsoft.ico`

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Open it

GIMPOpen sourcereads and writes · GNU General Public License, version 3.0
ImageMagickOpen sourcereads and writes · ImageMagick License
PhpThumbOpen sourcewrites · GNU General Public License
Q141647655Open sourcereads and writes · Apache Software License 2.0 / MIT License
Q847465Open sourcewrites · GNU Lesser General Public License, version 2.1 or later
AbydosOpen sourcereads · GNU Lesser General Public License
ConverseenOpen sourcereads · GNU General Public License, version 3.0
imageioOpen sourcereads · 2-clause BSD License
OpenImageIOOpen sourcereads · BSD licenses
PhotoRecOpen sourcereads · GNU General Public License
PixenOpen sourcereads · MIT License
Q130252332Open sourcereads · Apache Software License 2.0 / Creative Commons Attribution 4.0 International / MIT License
Acorn Image Editorreads and writes
Asepritereads and writes · proprietary license
Hijaak Digital Photo Studioreads and writes
IrfanViewreads and writes · freeware
Mathematicareads and writes · proprietary license
Microsoft Developer Studiowrites
Microsoft Paintreads and writes · proprietary license
Microsoft Visual Studio 2005 Team Suitewrites
Photopeareads and writes
Riptide Photo Studioreads and writes
Snagit 8reads and writes
Zoner Photo Studioreads and writes
ABViewerreads
ACD FotoCanvas Litereads
ACDSeereads · proprietary license
ACDSee 5reads
Adobe Captivatereads
Adobe Premiere Proreads · proprietary license
ArchiCADreads · proprietary license
CoffeeCup Softwarereads
CorelDRAW Graphics Suitereads
Fast Picture Viewerreads
FastStone Image Viewer 5.2reads
Graphic Workshopreads
Microangelo Toolsetreads
Microsoft Expression Media 2reads
Microsoft Photosreads · Microsoft end-user license agreement
Paint 3Dreads

And 4 more in the JSON record.

Convert it

To	With	Fidelity	Command and losses
Portable Network Graphics	ImageMagick	Lossless	`convert in.ico out.png` Pixels kept; some metadata, colour profiles or layers may be dropped.
Tagged Image File Format	ImageMagick	Lossless	`convert in.ico out.tif` Pixels kept; some metadata, colour profiles or layers may be dropped.
GIF 89a	ImageMagick	Lossy	`convert in.ico out.gif` Reduced to 256 colours.
JPEG File Interchange Format 1.02	ImageMagick	Lossy	`convert in.ico out.jpg` Lossy compression.
WebP	ImageMagick	Lossy	`convert in.ico out.webp` Lossy compression.

Documentation

kaitai grammar: https://github.com/kaitai-io/kaitai_struct_formats/blob/master/image/ico.ksy

Sources

From Converters (FFmpeg, ImageMagick, Pandoc, LibreOffice), Just Solve the File Format Problem (File Formats Wiki), Kaitai Struct format gallery, PRONOM, Wikidata. Updated 2026-10-24.

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