What are QR codes and how do they work?
A QR code is a two-dimensional barcode. Where a classic barcode holds a dozen digits on a single line, that black and white square holds up to 4,296 characters. That is far more than enough for a URL, a phone number or a contact card.
The three large squares in the corners act as markers. They tell the camera how the code is oriented, even if the phone is held at an angle or the surface is tilted. The rest of the area carries the data, plus an error correction zone that tolerates up to 30% damage.
In practice, the phone is only reading a link. It decodes the image, pulls out the URL, then shows a notification on screen. You tap it and the browser opens the page. Nothing is downloaded, nothing is installed. If you want the technical detail of how the decoding works, the article on how a qr code works walks through every step.
How to scan a QR code on iPhone
Scanning has been built in since iOS 11, released in 2017. In other words, every model still in service can do it: iPhone 11, iPhone 12, iPhone 14, iPhone 15 and later. There is no scanner app to install.
With the camera, in three seconds
- Open the Camera app from the home screen.
- Point the lens at the code, about 20 cm away.
- Wait for the yellow banner showing the website address.
- Tap it to open the page.
If nothing happens, check one setting: Settings, then Camera, then Scan QR Codes. The switch needs to be on. It is on by default, but a company restriction or an old change of settings can have turned it off.
Scanning a QR code from a photo or a screenshot
Sometimes the code arrives in an email or in a photo sent by message. Open the image in Photos and press and hold on the square: iOS detects it automatically and offers to open the link. Live Text does the same job with text and phone numbers.
The Control Center scanner
iOS also includes a dedicated Code Scanner. Add it through Settings, Control Center, Code Scanner. It opens a full-screen camera without the photo controls around it. Handy in low light, since the torch button sits right there in the interface.
How to scan a QR code on Android and Samsung
On a recent Android device, the logic is the same. Android 9 and later can read QR codes without a third-party app, provided the manufacturer has enabled the option.
On Samsung Galaxy
Open the Camera app, point it at the code, let it focus. A bar appears at the bottom of the screen with the address. If nothing shows up, go into the camera settings and turn on Scan QR codes. Samsung also puts a shortcut in the notification panel: swipe down twice, then look for the dedicated tile. Bixby Vision does the same job on older models.
On other Android devices
Google Lens is the universal scanner across the ecosystem. It is built into the Google app, into Chrome and often into the camera itself. Tap the lens icon, point, and the content appears. Lens can also analyse an image already saved in the gallery, which covers the screenshot case.
Over nearly two years of watching this play out in the dining room, customers asking for help almost always have a problem with light or distance, never with a missing app. The phone knows what to do; it is the stand that is badly placed.
Scanning a QR code free, online or on a computer
Scanning is free in every case. Paid apps on the Play Store or the App Store charge for extras: scan history, exports, code creation. For a simple menu, they add nothing.
On a computer, there are two options. Online reader websites let you drag an image into a drop zone and return the URL held in the code. On serious services the file stays in the browser, with nothing sent to a server. Otherwise, a PC or Mac with a webcam can read a code held up to the camera, as long as you allow access.
| Device | Method | App to install | From a photo |
|---|---|---|---|
| iPhone (iOS 11 and later) | Camera app or Code Scanner | None | Yes, press and hold in Photos |
| Samsung Galaxy | Camera or notification panel tile | None | Yes, via Gallery or Lens |
| Other Android device | Camera or Google Lens | None on Android 9 and later | Yes, with Lens |
| PC or Mac | Online reader in the browser or webcam | None | Yes, drag and drop the image |
My QR code will not scan: the real causes
A failed scan rarely comes from the phone. Here is what blocks it most often, in the order we see it happen in the dining room.
- The code is too small. Allow at least 2.5 cm per side for a scan at 30 cm. Below that, the camera stops locking on.
- The surface reflects light. Glossy plexiglass under a spotlight creates a glare that wipes out part of the pattern. A matte finish solves it.
- There is not enough contrast. A light grey code on a beige background scans badly. Stick to dark on light, never the other way round.
- The lens is dirty. A wipe with a cloth fixes it one time in three.
- The white margin has been trimmed. The square needs a quiet zone around it, about four modules wide.
Official documents are a separate case. For France Identité or an administrative certificate, the code uses a signed format that the camera can read but cannot interpret. You have to go through the dedicated app, the only one that can verify the signature.
What this means for a restaurant
The point to take away as a restaurateur: none of your customers needs to install anything. It is the number one objection you hear in the dining room, and it has been groundless since 2019 for the vast majority of phones in use. A guest who hesitates needs one sentence, not an instruction sheet: point the camera, the menu appears.
The real lever is elsewhere. The page that opens has to be light, load in under two seconds on an average mobile connection and stay readable without zooming. A PDF menu means pinching the screen ten times; that is where the customer gives up, not at the scan. A qr code menu built for mobile avoids that drop-off.
Two practical settings are worth the effort. First, print the code at 3 cm minimum on a matte table stand rather than on the tablecloth. Second, check that the page is reachable without forcing a Wi-Fi connection: asking for a password before anyone can scan adds one step too many. The tracking features then let you see how many scans actually turn into someone reading the menu.
Data security: is there anything to worry about?
A QR code contains no program. It cannot install software or collect information on its own. The risk lies in the link: a fraudulent sticker placed over yours redirects to a fake payment site. The practice has a name, quishing, and it mainly targets car parks and charging stations.
Two habits are enough. Read the URL shown before tapping, and check that the domain name matches the business. In the dining room, run your hand over your stands once a week: an added sticker can be felt with a finger. Codes printed directly onto the stand, with no label stuck on top, cut that risk sharply.