Good to know
Why “free” QR codes stop working
Many QR generators create dynamic codes: the code points to their redirect server, which then forwards people to your link. That lets them switch your code off when a trial ends — after you have printed 500 flyers.
A static code has no middleman. The destination is encoded in the black and white squares themselves, so there is nothing to switch off. The trade-off is that you cannot change the destination after printing — so check the link before you hit download.
For print, use the highest damage tolerance: it adds redundancy so the code still scans when it is scratched, folded or partly covered by a logo.