Website QR codes — Verify the result

Worked example

Scan the exported file with two phones and a raw-text reader, compare the address character by character, and test at print size.

A QR file is verified by reading it back, not by looking at it. Decode the exported image and compare the address it gives with the one you typed, character by character, including the scheme, the case of letters in the path and any trailing slash.

For the example https://example.com/guide, open the downloaded chatcument-qr.png on a screen and scan it with the stock camera app of one iPhone and one Android phone, then with a dedicated scanner app that prints the raw text. The camera should offer a banner for example.com/guide; the scanner should show the whole string. Wrong host, missing path or an added space means the content was altered before encoding, so fix the field and export again.

Check the file itself next. The PNG at the default setting should be 720 by 720 px; an export at 1440 should report 1440 by 1440. Open the SVG in a browser and zoom to 400 percent: edges stay crisp. A blurry PNG that looks fine on the screen will often fail once enlarged on paper, so judge the size that will actually be printed.

The mistake to avoid is scanning only on the monitor where the code was made. Print one on the real paper, set it where it will hang, and scan it from the intended distance, which is usually about ten times the code width, so a 3 cm code is read from around 30 cm. Test in the lighting of the room, with the same phones your visitors might use.

Finally, load the destination page after scanning: it should open over HTTPS without a warning, and the page that appears should be the one the card promises. Record the date, the address and the file name in a note so the test can be repeated.

https://example.com/guide

QR encoding the same URL

A visible code is not a verified code; only a scan of the real exported file, at print size, proves the address inside.