The YouTube Channel Icon size (800×800px)
YouTube recommends a 800x800 pixel square for your channel icon, displayed as a circle. This icon shows up next to every video, comment, and on your channel page, so a clean 1:1 upload at this resolution keeps it sharp everywhere and avoids the blur of an upscaled small file.
Since YouTube masks the square into a circle, the corners are cropped off. A logo or face pushed into a corner gets clipped, so keep your mark centered with a little padding so it sits comfortably inside the circle. This is especially important because the icon reinforces channel identity on every single video you publish.
In watch pages and comments the icon renders small, so simple wins. A bold logo, a single clear symbol, or a well-lit face reads instantly, while a detailed image collapses into noise. Uploading at the full 800x800 also means the icon still looks crisp on your channel page header where it displays larger, covering both extremes of its display size.