When people say “QR code” they mean one thing: the square with three corner marks that every phone reads. Its formal name is QR Code Model 2. Around it sits a family of relatives, some in the same international standard, some owned by the original inventor Denso Wave, and one recent addition designed for people with low vision. This article introduces each one and says plainly which your phone can read.
The one you know: Model 2
- Version 3, 29×29 modules, error correction M, mask 2. Tap a label to isolate it.
Model 2 is the 1997 revision of the original design. It added alignment patterns, so a code photographed at an angle or on a curved surface can still be read, and extended the range to 40 versions, from 21 to 177 modules a side. It is the code defined in ISO/IEC 18004, most recently revised in August 2024 (iso.org). Every phone camera app, every scanner app and every till that says it reads QR reads Model 2.
Model 1: the original
The 1994 original ran to version 14, or 73 modules a side, and had no alignment patterns. Instead it carried extension patterns along the right and bottom edges. It is obsolete. Denso Wave still lists it, but no encoder you are likely to use produces it and phone support is not something to rely on. If you find a Model 1 code in the wild it is a museum piece.
Micro QR
Micro QR, introduced in 2004, has a single finder pattern in the top-left corner and a quiet zone of only two modules instead of four. It comes in four sizes, M1 to M4, from 11 to 17 modules a side. The largest, M4, holds 35 digits, 21 alphanumeric characters, 15 bytes or 9 kanji, which is less than a version 1 QR code. M1 has no error correction at all; M2 and M3 offer levels L and M; M4 adds Q (Denso Wave).
Where it lives: circuit boards, small electronic parts and tool marking, mostly in Japan. Where it does not live: on anything the public scans. At the time of writing the iPhone Camera app does not decode Micro QR, and support in Android camera apps is patchy. Some dedicated scanner apps read it.
rMQR: the rectangle
Rectangular Micro QR, or rMQR, was standardised as ISO/IEC 23941 in 2022 (iso.org). It keeps a full finder pattern in one corner and a smaller mark in the opposite corner, with the data in a strip between. Sizes run from R7×43, 7 modules tall by 43 wide, up to R17×139. The largest holds 361 digits (Denso Wave). There are 32 sizes in all (from our reading of the standard; not confirmed on Denso Wave’s page).
The point of rMQR is space. A code 7 modules tall fits on the side of a syringe, a cable label or the edge of a blister pack where a 21-module square cannot. Japan’s medicine packaging is the showcase use. Phone support is thin: the open-source ZXing-C++ library decodes it and a few apps build on that, but camera apps from Apple and Google do not, as far as we can verify.
In practice
If you need a narrow code that phones can read today, use a small ordinary QR code and accept the square shape. Save rMQR for labels read by your own scanners.
iQR
iQR is a 2008 Denso Wave design that is not an ISO standard. It comes square or rectangular, from 9×9 modules holding 6 digits to 422×422 holding about 40,000 digits, or 5×19 to 43×131 in the rectangular form. Denso Wave says it can be about 30% smaller than a QR code for the same data, or hold 80% more at the same size, and offers error correction up to 50% (Denso Wave). It can also be printed inverted or as dots.
It needs a Denso Wave reader or licensed software. We found no evidence of phone camera app support. It is a factory and logistics code.
Frame QR
Frame QR, from 2014, reserves a canvas area in the middle of the code for a picture, logo or text. Unlike a normal QR code with a logo, which survives only because error correction repairs the covered modules, the canvas is part of the design and costs no repair budget. The code’s frame can be a square, a circle or other shapes.
It is a Denso Wave design and needs a compatible reader or SDK. We could not reach Denso Wave’s Frame QR page at the time of writing, so treat the details here as unverified and check the current page before relying on them. For a public-facing code with a logo, an ordinary QR code at level H does the job on every phone.
SQRC
SQRC looks exactly like an ordinary QR code and stores two things at once: a public part and a private part. Denso Wave says the private part “can be read only by specific types of scanners” and is meant for storing private information or managing a company’s internal data. Denso Wave also states plainly that the feature does not guarantee the coded data is secure (Denso Wave). Whether an ordinary phone reads the public part is not stated on that page; the design intent is that it does, but we have not verified it.
A typical use is a staff pass: the public part holds a name and the private part an employee number that only the company’s readers can see.
Accessible QR (NaviLens)
The NaviLens Accessible QR Code is a high-contrast coloured marker that wraps a conventional QR code. The NaviLens app finds the marker from up to 12 times the distance of a normal QR code, without needing to focus or frame it, in low light and at steep angles, and reads the content aloud. Because a standard QR code sits inside the marker, any phone camera still reads the ordinary code (NaviLens). The town of Kaminoyama in Japan put it on its municipal magazine so that residents with low vision could use it.
This is the variant to know if you make signage for public buildings or transport. The European Accessibility Act has applied since June 2025, and a code a blind person can find from across a hall is a practical way to meet it.
Apple App Clip Codes
Not a Denso Wave design, but part of the family in practice. An App Clip Code is Apple’s circular code, introduced with iOS 14, that launches a lightweight part of an app without installing it. It can be scanned with the iPhone camera or tapped as NFC. It is made with Apple’s generator tool and works only on iPhone (Apple). Android phones cannot read it, so any public placement needs an ordinary QR code beside it.
Side by side
| Variant | Shape and size | Capacity (max) | Standard | Phone camera app reads it |
|---|---|---|---|---|
| Model 2 | Square, 21 to 177 modules | 7,089 digits, 2,953 bytes | ISO/IEC 18004 | Yes, all |
| Model 1 | Square, 21 to 73 modules | About 1,167 digits (unverified) | Historic | Not reliably |
| Micro QR | Square, 11 to 17 modules, one finder | 35 digits, 15 bytes | ISO/IEC 18004 | Rarely; some apps |
| rMQR | Rectangle, 7×43 to 17×139 modules | 361 digits | ISO/IEC 23941 | Rarely; some apps |
| iQR | Square 9 to 422, rectangle 5×19 to 43×131 | About 40,000 digits | Denso Wave | No |
| Frame QR | Square or shaped, canvas in the middle | Not verified | Denso Wave | No (unverified) |
| SQRC | Square, looks like Model 2 | Public part plus private part | Denso Wave | Public part only (unverified) |
| Accessible QR | Coloured marker around a Model 2 code | As the code inside | NaviLens | The inner code, yes; the marker needs the NaviLens app |
| App Clip Code | Circle | A short URL | Apple | iPhone only |
Three ways this plays out in practice:
- A hospital labelling blood tubes. rMQR on the tube, read by the lab’s own scanners, because a square code will not fit the label width.
- A council putting wayfinding on a station. An Accessible QR marker, because the ordinary code inside works for everyone and the marker works for people who cannot see it.
- A café putting a code on the table. Model 2, level M, no exceptions.
Common mistake
Buying a generator that advertises Micro QR or rMQR for “smaller codes” and using it for the public. Smaller squares are no use if the phone does not know to look for them.
▸Why the variants are hard to add to phone cameras
A phone camera app looks for the 1:1:3:1:1 finder pattern in three places, then checks the geometry. Micro QR has one finder, so the app needs a second search strategy and a way to tell a lone finder from a corner of an ordinary code cut off by the picture edge. rMQR has one finder and one smaller sub-finder, in 32 aspect ratios. Each extra symbology costs processing time on every frame, whether or not any such code is ever in front of the lens, and raises the false-positive rate. Apple and Google have so far judged the trade not worth it for the built-in camera. Libraries such as ZXing-C++ support rMQR and Micro QR, so a dedicated scanner app can add them at the cost of speed.
Try it yourself
Type a short message and look at a version 1 Model 2 code: 21 modules, three finders, no alignment pattern. Then imagine the Micro QR M4 for the same text at 17 modules with one finder, and consider how much the phone would have to guess.