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# Exposure Notification

Implement a COVID-19 exposure notification system that protects user privacy.

## Overview

Use the Exposure Notification framework to inform people of potential exposure to COVID-19, the disease caused by the SARS-CoV-2 virus. You can build a notification system that employs random, rotating keys and identifiers to convey positive diagnoses in addition to data such as associated symptoms, proximity, and duration.

### Establish User Roles

The ExposureNotification framework defines two user roles:

- Affected user: When a user has a confirmed or probable diagnosis of COVID-19 (as defined by the Health Authority), the framework identifies them as *affected* and shares their diagnosis keys to alert other users to potential exposure.
- Potentially exposed user: To assign a user the *potentially exposed* role, use the framework to determine whether a set of temporary exposure keys indicate proximity to an affected user. If so, the app can retrieve additional information such as date and duration from the framework.

> Important:
> Before you can develop an app that uses ExposureNotification, you need the <doc://com.apple.documentation/documentation/BundleResources/Entitlements/com.apple.developer.exposure-notification> entitlement. For more information on this entitlement, see [Exposure Notification APIs Addendum](https://developer.apple.com/contact/request/download/Exposure_Notification_Addendum.pdf). To get permission to use this entitlement, see [Exposure Notification Entitlement Request](https://developer.apple.com/contact/request/exposure-notification-entitlement).

### Identify Your App’s Region

All EN apps must specify the region for which they work by adding a key called <doc://com.apple.documentation/documentation/BundleResources/Information-Property-List/ENDeveloperRegion> to the app’s `Info.plist` file. The value for `ENDeveloperRegion` is set to a string that represents the app’s region. This value can be an ISO 3166-1 country code (for example, “CA” for Canada), or the ISO 3166-1/3166-2 country code plus subdivision code (“US-CA” for California).

Explicitly set the associated domain link to your region code. Avoid using wildcards because they can impact system operations. See <doc://com.apple.documentation/documentation/BundleResources/Entitlements/com.apple.developer.associated-domains> for more information.

### Specify Exposure Notification API Version

iOS 13.7 introduces a new method of calculating the user’s Exposure Risk Value, described in [`ENExposureConfiguration`](/documentation/ExposureNotification/ENExposureConfiguration). Apps can implement this new method, or continue to use the calculation method introduced in earlier versions of iOS. To choose your app’s approach, add an entry to your app’s `Info.plist` file with a key of <doc://com.apple.documentation/documentation/BundleResources/Information-Property-List/ENAPIVersion>. To use the new approach, specify a value of `2`. To use the original approach, specify a value of `1`.

### Support Exposure Notification Express

Starting with iOS 13.7, Health Authorities can inform users of potential exposure to COVID-19 without a dedicated Exposure Notification app. This feature is called Exposure Notification Express and must be enabled by a Health Authority. For more information, see [Supporting Exposure Notifications Express](/documentation/ExposureNotification/supporting-exposure-notifications-express).

## Topics

### Essentials

[Supporting Exposure Notifications Express](/documentation/ExposureNotification/supporting-exposure-notifications-express)

Configure servers to notify users of potential exposures to COVID-19 without an app.

[Building an App to Notify Users of COVID-19 Exposure](/documentation/ExposureNotification/building-an-app-to-notify-users-of-covid-19-exposure)

Inform people when they may have been exposed to COVID-19.

[Setting Up a Key Server](/documentation/ExposureNotification/setting-up-a-key-server)

Ensure that your server meets the requirements for supporting Exposure Notifications.

[`ENManager`](/documentation/ExposureNotification/ENManager)

A class that manages exposure notifications.

  <doc://com.apple.documentation/documentation/BundleResources/Information-Property-List/ENDeveloperRegion>

  <doc://com.apple.documentation/documentation/BundleResources/Information-Property-List/ENAPIVersion>

[Changing Configuration Values Using the Server‑to‑Server API](/documentation/ExposureNotification/changing-configuration-values-using-the-server-to-server-api)

Update Exposure Notifications configuration values from a Public Health Authority’s server.

[Testing Exposure Notifications Apps in iOS 13.7 and Later](/documentation/ExposureNotification/testing-exposure-notifications-apps-in-ios-13-7-and-later)

Perform end-to-end validation of Exposure Notifications apps on a device by manually loading configuration files.

[Supporting Exposure Notifications in iOS 12.5](/documentation/ExposureNotification/supporting-exposure-notifications-in-ios-12-5)

Prepare your Exposure Notifications app to run on a previous version of iOS.

### Exposures

[Configuring Exposure Notifications](/documentation/ExposureNotification/configuring-exposure-notifications)

Define how Exposure Notifications work for a region by assigning server-based key-value pairs.

[`ENExposureConfiguration`](/documentation/ExposureNotification/ENExposureConfiguration)

The object that contains parameters for configuring exposure notification risk scoring behavior.

[`ENExposureWindow`](/documentation/ExposureNotification/ENExposureWindow)

A set of scan events from observed beacons within a time span.

[`ENScanInstance`](/documentation/ExposureNotification/ENScanInstance)

The aggregation of attenuations of beacons received during a scan.

[Exposure Parameter Limits](/documentation/ExposureNotification/exposure-parameter-limits)

The limits for the parameters you use in exposure risk calculations.

### Summaries

[`ENExposureDetectionSummary`](/documentation/ExposureNotification/ENExposureDetectionSummary)

A summary of exposures.

[`ENExposureDaySummary`](/documentation/ExposureNotification/ENExposureDaySummary)

The summary of exposure information for a single day.

[`ENExposureSummaryItem`](/documentation/ExposureNotification/ENExposureSummaryItem)

The summary of exposures for a specific time period or report type.

### Status

[`ENAuthorizationStatus`](/documentation/ExposureNotification/ENAuthorizationStatus)

A set of cases that indicates the authorization status for the app.

[`ENStatus`](/documentation/ExposureNotification/ENStatus)

A set of cases that represents the overall status of exposure notification on the system.

### Errors

[`ENError`](/documentation/ExposureNotification/ENError)

Errors that the exposure notification framework issues.

[`ENError.Code`](/documentation/ExposureNotification/ENError/Code)

Error codes that the exposure notification framework issues.

[`ENErrorDomain`](/documentation/ExposureNotification/ENErrorDomain)

The domain for an error.

[`ENErrorHandler`](/documentation/ExposureNotification/ENErrorHandler)

The handler for error conditions.


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