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I was using Kaspersky QR Scanner, but it seems to be limited to < 1000 chars or so in the QR code, even though QR codes can hold nearly 8000 chars. I'd like a secure QR code app which can do up to the max chars. It must run on Android, but ideally would work on iPhone too.

What I mean by "secure":

I don't want the chance of the read QR code content leaving my phone. That means I expect it to be processed on my phone only, not sent to the cloud, and not stored in any remote servers. I want no chance that the writers of the app can see the contents of the QR code, as it could contain private data, encryption or authentication keys, etc.

Here is a test QR code I'd like the application to be able to open:

enter image description here

This QR code contains all 2900 characters of my git-branch_.sh script file in my eRCaGuy_dotfiles repo.

I generated it using this command, as I describe here: How to best create QR Codes in Linux, including Ubuntu:

cat "eRCaGuy_dotfiles/useful_scripts/git-branch_.sh" \
| qrencode -m 4 -o /tmp/qr.png && eog /tmp/qr.png &

Despite being only 2900 chars, I can't even find a QR reader that will properly read it. I need a reader that will read it.

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2 Answers 2

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If privacy is an important factor for you you may want to look at the Privacy friendly QR code reader.

In my opinion it is not the best QR code reader app but it should perfectly fit your needs:

  • it is open source
  • Also available in F-Droid store
  • requires one permission: access the camera which means the app has no internet permission. This means it can not send anything to a server on the internet invisible in background
  • the description text mentions QR codes up to 7000 characters
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  • I'll try it out. Thanks! Official link to the maker's website: secuso.aifb.kit.edu/english/QR_Scanner.php Feb 1, 2022 at 21:24
  • It fails to read my test QR code. I'll post it later so others can try. Feb 1, 2022 at 21:29
  • Robert, I added a test QR code to my question. This app won't read that QR code. Feb 1, 2022 at 23:41
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    @GabrielStaples I realize this comment is a bit late, but perhaps you can send your QR code to the app's author so they can improve their open source tool? Or perhaps you can even help submit a patch? Oct 3, 2023 at 6:04
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The LEADTOOLS Barcode Reader App can read all 2900 characters from this QR code, as shown in the image below. (Disclosure: I work for its vendor).

LEADTOOLS Barcode App

The app does NOT send anything outside your device unless you press the “Web Search” button after recognition. Furthermore, you can modify the app’s source code (or build your own app) using the LEADTOOLS Barcode SDK and retrieve the data as a string, which you can process according to your application needs.

The SDK has a free evaluation here. If you install it, the App’s code is in the folder LEADTOOLS22\Examples\Barcode\Xamarin where the same project code can be used to build the app for both Android and iOS.

Please note that the QR spec does not allow 8000 characters into one barcode. The maximum for alphanumeric data is 4296 characters, as mentioned here.

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