Icon Sizes
ico-sizes
The ico-sizes parameter packs several sizes into a single fm=ico file. ICO is the one output format that can hold more than one image, which is what lets a single favicon.ico serve a browser tab, a bookmark bar and a desktop shortcut at their native sizes instead of a scaled one.
Pass up to 8 comma-separated sizes, each from 1 to 256. Every value is a target size in pixels for the icon’s longer edge:
https://assets.imgix.net/examples/blue-pineapple-no-background.png?fit=crop&ar=1:1&fm=ico&ico-sizes=16,32,48That request produces one file holding all three images below, each shown here at its real size.
ico-sizes=16
ico-sizes=32
ico-sizes=48
Accepted values
Invalid input is never an error — unusable values are dropped and the rest of the request is honored.
| Input | Result |
|---|---|
ico-sizes=48 | A single 48 px entry |
ico-sizes=16,32,48 | Three entries in one file |
ico-sizes=16,16,32 | Duplicates collapsed, so two entries rather than three |
ico-sizes=16,300,32 | Values outside 1–256 dropped, leaving two entries |
| More than 8 sizes | Only the first 8 are kept |
ico-sizes=abc | Unparseable, so one icon at the output size |
No ico-sizes | One icon at the output size |
Aspect ratio
Aspect ratio is preserved rather than forced square, so a wide logo packed at 48 is 48 px on its longer edge — ico-sizes=16,32,48 on a 3:2 source gives entries of 16x11, 32x21 and 48x32. For true square icons, crop the source first with fit=crop and a square ar, as the example above does.
ico-sizes does not appear in the X-Imgix-Params response header.