Downloading a code, and which format to use

PNG, SVG, PDF, EPS, JPG, GIF — and what a printer actually wants.

For a screen

PNG. Set the size to at least twice the pixel width it will be displayed at, so it stays sharp on a dense screen.

For print

SVG, PDF or EPS. All three are vector: they scale to any size with no loss, which is what a print shop needs. Set the width in millimetres rather than pixels and the file arrives at the physical size you asked for.

PDF and EPS can be exported with CMYK colours where your printer requires them.

The quiet zone

The empty margin around a code is part of the code. Do not crop it, and do not put anything in it. Exports include it; a designer trimming "the white space" is the most common reason a printed code stops working.