'How do you combine multiple (different) images into a single favicon?

There are lots of services that will take an image and create every size of web icon out of it by downscaling it to the appropriate resolutions.

However, I have designed two favicons specifically for their resolution (16x16 and 32x32), which means I have two separate, different pngs. I would love to combine these icons into one favicon.ico so I can serve that file properly. Anyone know how one could accomplish this?



Solution 1:[1]

An older site, but this is the only online service I've found in 2022 which allows you to upload files for specific sizes, then merge them into an ICO:

https://www.xiconeditor.com/

Supports 64x64, 32x32, 24x24 and 16x16

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Solution Source
Solution 1 Shaw