When you start a YouTube channel from scratch, your channel icon will be linked to your brand account’s profile photo. To change it, YouTube will direct you to update your brand account.
It’s recommended that your picture be a JPG, BMP, PNG, or non-animated GIF, saved at 800 x 800 pixels. You should also make sure it displays well at smaller sizes and in both a square and a circle crop for the multiple places YouTube will use your channel icon.
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