Two modes. Banner: each line of text is drawn with a built-in 5×5 block font (letters, digits and common punctuation; other characters are listed as skipped) using the fill and spacing you choose, optionally doubled in size. Image: pick a picture and it is decoded inside the Worker, downscaled to at most 2048 px, and mapped to characters by brightness with a standard, detailed or block ramp, a chosen column width and optional inversion for dark backgrounds. Nothing is uploaded. Best viewed and pasted in a monospace font.