ICO Image (.ICO)
ICO is an image format used to store icons in Microsoft Windows and for website favicons. A single ICO file can contain multiple images at different sizes and color depths, allowing the operating system or browser to select the most appropriate version. ICO files support sizes from 16x16 up to 256x256 pixels with up to 32-bit color depth including alpha transparency.
Advantages of ICO Image
What the ICO format does well, and why you might choose it.
- Can store multiple resolutions and color depths in a single file
- Universal support as favicons in all web browsers
- Native format for Windows application and system icons
Limitations of ICO Image
What the ICOformat doesn't do well, and when to choose another format.
- Limited to relatively small image dimensions (max 256x256)
- Larger file sizes than PNG when embedding multiple resolutions
- Primarily Windows-centric with less relevance on other platforms
What ICO files are used for
- Website favicons displayed in browser tabs and bookmarks
- Windows application and shortcut icons
- Desktop and toolbar icons in Windows environments
How ICO files work
Raster images are grids of pixels, each carrying color information. The format determines how those pixels are stored: lossless formats (PNG, TIFF, BMP, WEBP-lossless) preserve every pixel exactly, lossy formats (JPG, WEBP, AVIF, HEIC) discard imperceptible detail to shrink the file. Color depth (8-bit, 10-bit, 16-bit), color profile (sRGB, Display P3, ProPhoto), alpha channel support, and metadata (EXIF, IPTC, XMP) all vary by format. Modern web formats like AVIF and WEBP build on improvements in video compression to deliver dramatically smaller files at equivalent quality versus JPG and PNG.
Best practices when working with ICO
Photographs compress well as JPG or AVIF; graphics with sharp edges, text, or transparency belong in PNG or WEBP-lossless. Never re-save a JPG repeatedly — every save adds compression artifacts. Strip EXIF metadata before publishing photos publicly if you don't want GPS coordinates and camera serial numbers exposed. For print, deliver in TIFF at 300 DPI; for screen, JPG/WEBP at 72-100 DPI is plenty. If you're optimizing for the web, AVIF beats WEBP beats JPG on file size, but JPG still has the broadest support.
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Convert ICO to other formats
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Choosing ICO versus the alternatives
JPG: photographs, social media uploads, anywhere universal compatibility matters. PNG: graphics with text, line art, screenshots, or transparency. WEBP: modern web replacement for JPG and PNG with better compression. AVIF: best-in-class web compression, growing browser support. TIFF: print and archival masters. BMP: rarely the right answer in 2026 — uncompressed and uniform-poor versus PNG. HEIC: efficient mobile photo capture, but limited compatibility outside Apple's ecosystem.
Where ICO fits in real workflows
Most image workflows have a master file (PSD, RAW, TIFF) that you keep forever and never publish, plus delivery exports (JPG, WEBP, AVIF) generated for each context where the image appears. Treat published files as derivatives — if quality requirements change, regenerate from the master rather than re-converting an already-compressed version.
Privacy and file handling
When you convert a ICOfile with MegaConvert, the file is uploaded to our converter, processed, and automatically deleted within an hour. We don't train models on your files, share them with third parties, or retain them after the conversion completes. The download link expires when the file is removed. If your work involves files subject to NDA or compliance requirements (HIPAA, GDPR data processing), please review our privacy policy before uploading sensitive material.
Frequently asked questions about ICO
What is a .ICO file?
ICO is an image format used to store icons in Microsoft Windows and for website favicons. A single ICO file can contain multiple images at different sizes and color depths, allowing the operating system or browser to select the most appropriate version. ICO files support sizes from 16x16 up to 256x256 pixels with up to 32-bit color depth including alpha transparency.
What is the MIME type of ICO?
The official MIME type for ICO files is image/x-icon. This is the value web servers and applications use to identify the format when transferring files.
What category does ICO belong to?
ICO is a Image Converter format. Files in this category share common conversion paths and use cases.
How do I open a .ICO file?
ICO files are typically opened by software that natively supports the ICO Imageformat. If you don't have a compatible application, the most reliable approach is to convert the file to a more universal format using the converters listed above. Most ICO Image files convert to widely-supported alternatives in seconds.
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