Most QR code generators pull the old bait-and-switch ("free" until you hit 150 scans) then it's pay up or your code dies. OOPS, already printed it? Tough luck. Ours? No games, no ransom notes. Just free and unlimited. Forever.
Pro Tip: Keep your icon simple so it's clear (since it will be very tiny). Use a short URL. Long URLs make QR codes more complex, with smaller pixels that are harder to scan unless printed large.