Turn a link into a nonogram

A QR code is a grid of black and white squares, which is exactly what a nonogram hides. Type a link — or a few words — and the numbers along the edges write themselves. Whoever solves the board ends up with the code, and a phone reads it straight off the page: a surprise at the end of a puzzle, an invitation on a card, the last page of a puzzle book.

The same text can be written as a QR code in eight ways, and a phone does not care which; a nonogram does. Most of the eight leave a few cells that cannot be settled without guessing, and one of them usually leaves none — so the tool tries them all and keeps a board that can be solved line by line, at the highest error correction that fits, so a cell or two shaded wrong still scans. Keep the link short: the boards are 21, 25 or 29 cells a side. On paper, leave a margin of white around the board.