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A decentralised check-in system for meetings and events


The app is a decentralised check-in system for meetings and events. Users can check in to a venue by scanning a QR Code. The check in is stored locally and encrypted. In case one of the visitors tests positive subsequent to a gathering, all other participants can be easily informed via the app. The app uses the CrowdNotifier SDK based on the CrowdNotifier White Paper by Wouter Lueks (EPFL) et al. The app design, UX and implementation was done by Ubique. More information can be found here.

Try it now!

  1. Install the Android or iOS app. Download Android App Download iOS App
  2. Go to the QR code generator page and create your own Entry and Trace QR codes.
  3. Scan the QREntry with the app to check-in to your venue.
  4. Check out in the app after some time.
  5. Scan the QRtrace with any QR code reader and open the URL.
  6. Enter the time range for which you want to warn people who were at your venue and upload the data.

Work in Progress

The NotifyMe App system contains alpha-quality code only and is not yet complete. It has not yet been reviewed or audited for security and compatibility. We are both continuing the development and have started a security review. This project is truly open-source and we welcome any feedback on the code regarding both the implementation and security aspects. This repository contains the open prototype Application, so please focus your feedback for this repository on implementation issues.


All code can be found in the following repositories:

Further Documentation

The full set of documents for CrowdNotifier is at Please refer to the technical documents and whitepapers for a description of the implementation.


This project is licensed under the terms of the MPL 2 license. See the LICENSE file.


Overview of NotifyMe: A decentralised check-in system for meetings and events







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