Convert JPEG XL to ICO

JPEG XL (.jxl) is a modern image format standardized as ISO/IEC 18181 in 2022 by the Joint Photographic Experts Group. It supports both lossy and lossless compression, high bit depth, HDR, wide color gamuts, transparency and animation, and typically produces files 30–60% smaller than JPEG at the same visual quality.

A distinctive feature is lossless JPEG recompression: an existing JPG can be converted to JPEG XL about 20% smaller and converted back to the exact original bytes.

Support is still growing. Safari (macOS Sonoma, iOS 17 and later) displays JPEG XL natively, and so do Photoshop, GIMP, Affinity Photo, darktable and IrfanView. Chrome and Edge removed their experimental support, and Firefox only offers it in Nightly builds, so convert JXL to JPG or PNG when you need an image that opens everywhere.

The ICO format is an image container specifically designed for Microsoft Windows to store icons for executable files, folders, and applications. Introduced with Windows 1.0, it can encapsulate multiple raster images of varying dimensions and color depths (specifically BMP or PNG frames) within a single file to support dynamic scaling across different display resolutions. The structure comprises an ICONDIR header referencing one or more ICONDIRENTRY directory entries, allowing the operating system to select the appropriate 16x16, 32x32, or 48x48 pixel resource based on the current UI scaling settings.

ICO files are natively supported by the Microsoft Windows operating system, which automatically renders them in the File Explorer and taskbar. On macOS, Apple Preview handles the format natively. For editing or detailed inspection of the contained bitmap layers, raster graphics editors such as GIMP, Adobe Photoshop (via plugin), or Paint.NET are required. Web browsers also natively render ICO files when they are designated as favicons.