Each site has several icons in several formats. Make sure to include where you found the icon, the exact url and format.

Alternatively when asking about the [site](https://api.stackexchange.com/docs/types/site) type, include which of the url fields are at play:

- favicon_url
- high_resolution_icon_url
- icon_url

Note that `high_resolution_icon_url` got added in the 2.1 version.

If your question is about UI aspects, consider the tag [tag:logo] as well.