This decision matters less than people think, and the thing it is often confused with, where you put the target, matters much more. Still, there are real differences worth two minutes.

The practical differences

 Printed QR codeHousehold barcode
Setup effortGenerate and print itNone, scan what you own
Choose the exact locationYes, anywhere you can stick itLimited to where the object lives
Runs outNeverYes, when the product is finished
Someone else moves itUnlikely if stuck downCommon in shared kitchens
Scan speedFast, flat and high contrastSlower on curved bottles
Survives a damp bathroomOnly if taped or laminatedUsually fine
Ties into your routineOnly where you place itAttached to something you already use

When to print a QR code

Practical notes: print it large enough to scan quickly in poor light, tape or laminate it if it is going somewhere damp, and do not keep a copy of the image on the phone you are trying to get out of bed with.

When a household barcode is better

Choose something long-lived. A kettle, a soap dispenser or a tin you refill will outlast a toothpaste tube by years.

Use both

The setup that holds up best over months is a household barcode as your primary, in the room you actually want to be standing in, and a printed QR code as a backup in a different room. The barcode ties into your routine; the printed code covers the day the product runs out.

Mornio supports up to two backup items alongside the primary, so three codes total. Put them in different rooms rather than on the same shelf, since the failure you are covering is the primary being gone, not momentarily out of reach.

Does either one affect privacy?

Not in a well-built app, because neither is stored as a readable value. Mornio saves a salted one-way hash plus a label you choose, so nothing on the device reveals which product you scan or where it lives. That applies identically to printed codes and product barcodes. Other apps make different choices, so check the privacy policy if it matters to you.