Corona-Warn-App Open Source Project

Help us improve the Corona-Warn-App

The Corona-Warn-App is an app that helps trace infection chains of SARS-CoV-2 (which can cause COVID-19) in Germany. The app is based on technologies with a decentralized approach and notifies users if they have been exposed to SARS-CoV-2. Transparency is key to both protect the app's end-users and to encourage adoption.

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How it works Data privacy & security Our partners

Corona-Warn-App Smartphone

This is how the app works best

The RKI as the publisher of the app and the Federal Ministry of Health, in co-operation with Deutsche Telekom and SAP, are constantly reviewing possible further developments as well as incoming development proposals. This also includes whether further information can be integrated into the app, for example on the latest pandemic situation. For that purpose we will continue to intensively incorporate the information that we receive via the various channels into our development process. Here we have briefly summarized the most important tips for using the app:

  1. Download the current version of the app (iOS: 3.2.3 or Android: 3.2.1)
  2. Keep operating systems up-to-date (at least iOS 12.5 or iOS 13.5 depending on your iPhone model or at least Android 6 with current Google Play services)
  3. Keep background updates switched on and check them regularly
  4. To be on the safe side, open the app once a day

We recommend that you always ensure an adequate power supply.

You can find further information under Frequently Asked Questions about the Corona-Warn-App.

How does the app work?

  1. 01.

    Collect nearby identifiers

    The Exposure Notification System (by Apple and Google) on a mobile device broadcasts a Rolling Proximity Identifier (something to be remembered by), while also regularly scanning for identifiers of other phones using Bluetooth Low Energy technology and storing the identifiers locally. The identifiers are only valid for 10-20 minutes and are derived cryptographically from temporary keys which change every 24h.

    Too complicated? Here's a simple video explanation.
  2. 02.

    Communicate test result of user with symptoms (optional)

    If the lab in question supports the electronic process, tested users can use the QR code they received during the test to retrieve their results.

  3. 03.

    Distribute list of keys of SARS-CoV-2 confirmed users

    In case of a positive test result, users are asked to voluntarily upload their temporary keys of up to the last 14 days to the server. To prevent misuse, the Corona-Warn-App backend first verifies the positive test result. If confirmed, the server adds the user’s keys to the SARS-CoV-2 confirmed list, which is regularly broadcasted to all apps.

  4. 04.

    Check for exposure to SARS-CoV-2 confirmed users

    After a mobile device has downloaded the list of all available keys of users that have tested positive, the Exposure Notification System derives the corresponding identifiers and checks locally if any of these match the locally collected Rolling Proximity Identifiers. In case of exposure, the risk is assessed and the user receives corresponding instructions.

    Learn more in scoping document

Stay up to date!

on Jun 1 | by CWA-Team, 10:00 am

The Corona-Warn-App team says “Thank You!”

Read the Blog

on May 2 | by CWA-Team, 10:45 am

Which CWA functions end – and how you can still use the app

Read the Blog

on Apr 19 | by CWA-Team, 1:00 pm

Version 3.2 of the Corona-Warn-App available

Read the Blog

Join the open-source project!

If you want to contribute, head over to GitHub to get started.

You can also read the documentation, learn about our Code of Conduct and find out how to contribute on the Community page.

Contribute on GitHub

Data privacy and security

Open source approach

  • Transparency

    Only through transparency can we earn the trust of the end-users and increase app adoption. Our architecture document and the terms of use are openly accessible.
    Past versions of the respective terms of use can be viewed here.

  • Power of the community

    The power of the community increases security and data privacy protection by detecting issues early and helping to solve them.

Data Privacy and Safety

  • Decentralized approach

    The architecture follows a decentralized approach – based on the DP-3T and TCN protocols, as well as the Privacy-Preserving Contact Tracing specifications by Apple and Google.

  • You are in control

    You have full control over your data, you decide for which purposes your data is used. In the app, you define the functions and purposes you want your data to be used for and with whom the app is allowed to share your data. Unless you consent, the app will not transfer any data to third parties. And if you later change your mind, you can change your settings in the app any time.

  • Data Privacy documents

    Details are outlined in the privacy notice of the Robert Koch Institute. Additional insights are available in the Data Protection Impact Assessment (German only) and in the Legal Notice for iOS and Android (German only, find English version in app). Past versions of the privacy notice are still available.

  • Part of design

    It is part of the design process to ensure for each step that the app processes a minimum of required personal data that is handled with maximum protection.


  • Open and transparent

    No security through obscurity: we follow an open and transparent approach.

  • Secure Software Development Lifecycle

    Security assurance of application development through Secure Software Development Lifecycle, which includes among other things threat modeling and end-to-end risk assessment, security planning, security testing and penetration testing.

  • Secure hosting

    Hosting conform to BSI C5, SOC 2 and SOC1/ISAE 3402.

Our partners

Early May 2020, the German government requested SAP and Deutsche Telekom subsidiary T-Systems to deliver the official Corona-Warn-App for Germany, based on open source and a decentralized approach. The following partners are supporting the development of the app together with the involvement of the global open source community.

  • Boston Consulting Group
  • BCG Digital Ventures
  • Cispa
  • Detecon
  • Edelman
  • Fraunhofer Institut
  • Healthy Together
  • Helmholtz
  • msg systems ag
  • Robert Koch Institut
  • SAP
  • Telecom
  • TÜViT

Join the open-source project!

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