QR reader incorrect output


Our project uses QR code stickers to assign an ID to survey respondents, and the QR code reader on Kobocollect sometimes outputs the wrong ID (i.e., a string of numbers that is completely different from what the QR code should be). We have checked and there is no issue with the QR code sticker itself.

Additional details

This has been happening for different projects, on different devices, and since April 2021.

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Welcome to the community, @salomegarnier! Do you use the devices QR code reader or do you use an external app (device) to collect the QR code?

We have been using the default QR scanner in Kobo, no external apps. The issue is happening on both tablets and phone.

Is this an issue with only a single device or with other device too?

Several different devices.

And have you tried with the barcode?

Hi @Kal_Lam, hope you’re doing well!

Adding some details here since this is coming from a project I’m involved with.

For 2 seperate data collection projects, we are using printed QR labels with unique IDs to link data collected on blood samples and survey forms. We are using KoboCollect on both projects and one project uses smart phones and the other uses tablets for data entry. At this point, we have scanned 1,000’s of barcodes and this has happend maybe 10-15 times. We have tested the barcode and there is nothing wrong with the printed QR labels. The ones that showed the wrong ID code after scanning, worked correctly after scanning again. It has not been a major issue for us, since its only happened a handful of times, but wanted to report the issue since it seems like there may be a bug in the software.

Let us know if you need any other details. This may be a hard one to reproduce since it seems to happen at random and very rarely.

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Welcome back @mike.destaubin! Good to see you in the community. Thank you for the detailed description. So going through the details you provided, I feel like it could be an issue with the Collect android app. Adding @Xiphware in this post who should be able to see if it’s a bug related to the Collect android app.

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Hi @Kal_Lam and @Xiphware

Just want to follow up and add that it’s happening slightly more frequently now. We’re now getting incorrect QR readings in KoboCollect about 5-7 times a week. Still not a major issue for us to resolve, but wanted to provide an update.

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I’m not aware of any particular bugs in Collect at the moment that result in bad QR scans. But have you tried upping the error detection/correction level in your actual QR codes? It could just be some scans are so bad out in the field that the QR error correction cant detect & compensate. eg the following are the same URL, but have different error correction capabilities:



Latter should tolerate a successful scan under worst conditions, as it encodes more redundant info to detect/correct errors.

This is a good place to play around with QR codes and changing such parameters: QR Code and 2D Code Generator - Kerem Erkan