The little icon that you see in a broswer tab. But default, a switchless project will have the sailjs icon as favicon.
Use this service to generate a favicon - https://favicon.io/favicon-converter/
Use this service to make white area transparent - https://onlinepngtools.com/create-transparent-png
The default favicon in your switchless project will be at
assets/favicon.ico. The favicon that you download from favicon.io will contain favicons generated in various sizes. You want the 32x32 pixel version. Copy paste that image into
/assets and rename it as
favicon.ico to replace the favicon.