Do QR codes work on metal business cards?
On metal, a QR code fails for the same reasons it fails on paper: too little contrast, no clear margin, or modules too small to find. Here is how we check the QR on every Cardr Metal card before it is made, what that check found in every colour and layout, and the rules that make it pass.
Yes, when the engraving is made for a camera. Before any Cardr Metal card is made, we draw its back exactly as the laser will cut it and decode the QR. For the sample card on this page, all six decode to the address they carry, in all three colours and both layouts, as the metal looks to a camera and in the laser’s file. Phone scans of finished cards come when the supplier’s samples arrive.
- Silver and Gold
- Engraved and filled black, so the code is dark modules on light metal.
- Black
- Engraved to bare metal around the code, leaving the modules as the dark coating, so it still reads dark on light.
- Every card
- A 25 × 25 code at error correction Q, with 0.96 mm modules on the Classic layout and 0.77 mm on the Centred, and four modules of clear space round it.
By Kai, Founder of Cardr. Published . Sources checked .
Three colours, two layouts, every QR read.
Each row is the back of one sample card, drawn in one colour and layout by the code that draws the laser’s file, then decoded twice. The card is a sample, not a customer’s: Alex Morgan of Northway is the demonstration holder from our product page, and its code, SAMPLEU, can never be given to a real card, because real codes never use the letters I, L, O or U. Point a phone at one and it brings you back to this table.
| Card | Engraving | Camera view | Laser file |
|---|---|---|---|
| BlackClassic | Bare metal | Read | Read |
| BlackCentred | Bare metal | Read | Read |
| SilverClassic | Filled black | Read | Read |
| SilverCentred | Filled black | Read | Read |
| GoldClassic | Filled black | Read | Read |
| GoldCentred | Filled black | Read | Read |
Camera view is the card as a material, with its colour, brushed grain and sheen, decoded without allowing an inverted read. Laser file is the two-tone file the laser cuts from, decoded allowing one. Read means the decoder returned exactly HTTPS://CARDR.CO/Q/SAMPLEU, the address the code carries.
Drawn once, decoded twice.
The check is code, so it runs the same way on every card, every time. It proves the artwork. The phones come later.
- Draw the back. One function draws the preview on our product page, the proof a customer approves and the file the laser cuts from, so the check reads the drawing that is made.
- Turn it into pixels, at no fewer than 10 pixels to a module on the smallest code, so rounding never decides the result.
- Decode the camera view with jsQR, an open-source QR decoder, without letting it try an inverted read. A card that only read inverted would fail here.
- Decode the laser’s file, letting it try both ways round. On Black the laser cuts the panel and leaves the modules, so that file is the negative of the finished card.
- Pass only if both return exactly the address the code carries.
It runs on every real order too. The engraving page our maker works from decodes each pack’s own artwork with its own code, then confirms that the code is switched on and opens its holder’s profile. If any of that fails, the page says “Do not make this pack.”
What it cannot tell us. A render is not metal. The check proves the artwork is right; it cannot see how deep the laser cuts, how evenly a fill takes, or how a brushed surface catches a bright light. That is what the phone scan tests are for, once the samples arrive.
What keeps a QR on metal readable.
Five rules, and the numbers behind them. The millimetres are measured from the drawing the laser cuts. The error correction and margin figures are DENSO WAVE’s, the company that developed the QR code. DENSO WAVE, History of QR Code, checked
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01Dark on light, on every colour.
A QR code is dark modules on a light ground, and our check reads the camera view that way round only. So every Cardr Metal code is dark on light, whatever the colour of the card.
On Silver and Gold it is engraved and filled black. A bare laser mark on light aluminium is pale, too faint to rely on, so each module is cut and filled.
On Black the laser turns the colour to bare metal, which is bright. Engraving the modules would make a light code on a dark card, so we do the opposite: the laser clears a bright panel round the code and leaves the modules as the dark coating.
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02Modules big enough to find.
On the classic layout the code is 24 mm square and each module 0.96 mm. On the centred layout, where your details sit beside the code, it is 19.2 mm and 0.77 mm, so a long email address keeps its room.
How module size sets the printed size is worked through in what size a business card QR code should be.
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03A short address, in capitals.
The code holds a Cardr address, not your details: HTTPS://CARDR.CO/Q/ and a seven-character code, 26 characters in all. That is the same on every card, so the grid is 25 × 25 however much is engraved on the card itself.
It is in capitals because QR’s alphanumeric mode, which covers capitals, digits and a few symbols, including : / and ., packs them tighter. In lower case the same address needs a 29 × 29 grid at the same error correction, and every module gets smaller. Why a short link beats putting your details in the code is on QR code business cards.
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04Error correction Q.
A QR code carries spare data so it still reads when part of it is damaged, at one of four levels. We make every code at error correction Q, which DENSO WAVE puts at about 25% of the code’s data restorable. A card lives in a pocket, so the headroom goes on wear rather than on a smaller code. DENSO WAVE, Error correction feature, checked
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05Four modules of quiet zone.
DENSO WAVE puts it plainly: “QR Code requires a four-module wide margin at all sides of a symbol.” DENSO WAVE, Point for determining the code area, checked
On Black that margin is the engraved panel’s border: 3.84 mm on the classic layout and 3.07 mm on the centred, four modules each. On Silver and Gold it is untouched metal, and nothing else is engraved inside it.
| Classic | Centred | |
|---|---|---|
| Code size | 24 mm square | 19.2 mm square |
| Module size | 0.96 mm | 0.77 mm |
| Grid | 25 × 25 modules | 25 × 25 modules |
| Quiet zone | 3.84 mm, four modules | 3.07 mm, four modules |
| Error correction | Q | Q |
Real phones, not yet.
Phone scan tests: coming when supplier samples arrive
Everything above is our artwork, checked by code. None of it is a phone reading a finished card yet, because the supplier’s samples have not arrived. When they do, we will scan every colour in both layouts with real phones and publish each attempt here, the ones that fail included, with:
- Phone
- Operating system
- Camera app
- Colour
- Layout
- Light
- Distance
- Result
- Date
Cardr Metal. Your details engraved in anodised aluminium, and a QR that opens your live Cardr, checked like this before your pack is made. From £129 for 50 cards, with free UK delivery.
See Cardr MetalQR codes on metal, answered.
Do QR codes work on metal business cards?
They can, if the engraving is made for a camera: dark modules on a light ground, a clear margin four modules wide, and modules big enough to find. Cardr Metal does that on every colour, and we decode every card’s artwork before it is made. Phone scans of finished cards come when the supplier’s samples arrive.
Why do some QR codes on metal cards not scan?
Usually contrast. A bare laser mark on light aluminium is pale, so on Silver and Gold ours are filled black. On a dark colour, engraving the modules would make a light code on a dark card, the reverse of a printed QR, so on Black we engrave the margin round the code instead. The other usual causes are a code too small for its card and a margin too narrow.
Which colour of metal card scans best?
In our artwork check every colour decodes, in both layouts. We will not rank them until phones have scanned finished cards; those results go on this page, failures included, when the supplier’s samples arrive.
What happens if the card gets scratched?
Every code is made at error correction Q, which DENSO WAVE puts at about 25% of the code’s data restorable. That is headroom against wear, not a promise about any one scratch. DENSO WAVE, Error correction feature, checked
Can I change where the QR goes after the cards are made?
The QR holds a short Cardr address, not your details. It opens your Cardr as it is today, so you change your details there and every card you have handed out follows. You can also switch a pack’s code off from your dashboard.