Make a clean website favicon from a letter and two colors. Download it as favicon.ico and every PNG size browsers and phones ask for — plus the HTML to wire it up.
What sizes does a website favicon need? Browsers want a favicon.ico (16/32 inside one file) or a 32×32 PNG; phones want bigger: 180×180 for Apple home-screen icons and 192×192 for Android. The buttons above produce all of them from one design.
What makes a good favicon? One or two bold characters on a solid color, readable at 16 pixels. Fine detail disappears at tab size — if it does not read as a tiny square, simplify it.