Replace a QR Code in a Poster Without Breaking It

A poster goes to print with a QR code pointing at last year's registration page, or at a URL that has since moved. Replacing it looks trivial — cut out the old square, paste a new one — and then the printed sheet does not scan.

Almost every failure comes from one of three things: the new code was scaled by a fraction of a pixel, it lost its quiet zone, or it was generated at a different module count than the space allows.

In a hurry? The captions and labels around the code can be edited with RetypePic in a couple of minutes; the QR square itself needs the manual steps below.

Status note: RetypePic edits text areas. Swapping the QR square itself is a deterministic image operation, not a generative one, and it is not automated in the editor yet — this page documents the manual procedure that works, plus where the tool does help (captions and labels around the code).

1. Find out what the old code actually points at

Scan it with two different phones before you remove it. Printed codes are sometimes encoded with a shortener or a tracking parameter that you need to keep, and sometimes they point at a page that has already moved. Write the full URL down, including any query string.

If the old code still scans and points where you want, you do not need a new code at all — you need a redirect on the server, which costs nothing and cannot break the print.

2. Regenerate at the right module count

A QR code is a grid of modules. The square on the poster is a fixed physical size, so the question is how many modules fit in it without blurring.

1. Export the new code as PNG, black on white, no rounded corners, no logo overlay. Logos punch holes in the error-correction data and are the most common reason a good-looking code fails on paper.
2. Generate at error correction level M or Q. Higher levels survive more damage but leave fewer modules for the same physical size.
3. Keep the quiet zone: at least 4 modules of white on every side. If your old code had a white border baked into the artwork, reproduce it at the same proportion.

3. Size it in whole pixels, then place it

Do not drag a corner handle. A code resized by 63% ends up with modules that are 5.7px wide and get anti-aliased into grey smudges.

1. Measure the old square in pixels (in Photoshop, Figma or GIMP: the selection size, not the inch size).
2. Decide the module count you need, then scale the new PNG by a whole-number factor with nearest-neighbour resampling, so every module lands on exact pixel boundaries.
3. Paste it into the poster at the same coordinates as the old square, then export the poster at its original pixel dimensions.

If the new code has more modules than the old one, it will print denser in the same area. Below roughly 2mm per module on the finished print, phone cameras start to struggle — at that point, make the square bigger or shorten the URL.

4. Verify before it goes to print

• Scan the composed file on screen at 100%, then again at print size if you are proofing on paper.
• Scan with two different apps. One aggressive scanner can hide a code that half the audience cannot read.
• Check the quiet zone survived the paste. A code butted against dark artwork stops working in dim light.
• Confirm the target page opens on mobile, since that is where the scan lands.

5. The part RetypePic helps with

The QR square is rarely the only thing changing. A poster that carries a new registration link usually needs a new date, a new price or a new venue name in the text next to it — and that is exactly what the editor does, without touching the artwork around it.

Box the whole text line, type the old wording and the new one, and the output lands at the original pixel size. Open the editor to try it on your own file, or read the step-by-step walkthrough first.

Checklist

• Old destination URL recorded, including query string
• New code exported as PNG, no logo, level M or Q
• Quiet zone of at least 4 modules preserved
• Scaled by a whole-number factor, then positioned at the old coordinates
• Scanned on screen and on paper with two apps
• Adjacent text updated with RetypePic, original size preserved