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# NEURLFilterControlProvider

A protocol that defines an object that’s responsible for fetching pre-filter data.

```
protocol NEURLFilterControlProvider : AppExtension
```

## Overview

Create a class that conforms to this protocol in your app extension, then provide the extension’s bundle identifier to the [`NEURLFilterManager`](/documentation/NetworkExtension/NEURLFilterManager) in [`setConfiguration(pirServerURL:pirPrivacyPassIssuerURL:pirAuthenticationToken:controlProviderBundleIdentifier:)`](/documentation/NetworkExtension/NEURLFilterManager/setConfiguration(pirServerURL:pirPrivacyPassIssuerURL:pirAuthenticationToken:controlProviderBundleIdentifier:)).

## Topics

### Starting and stopping the provider

[`func start() async throws`](/documentation/NetworkExtension/NEURLFilterControlProvider/start())

Prepares the filter to start, in response to a call from the framework.

[`func stop(reason: NEProviderStopReason) async throws`](/documentation/NetworkExtension/NEURLFilterControlProvider/stop(reason:))

Prepares the filter to stop, in response to a call from the framework.

### Fetching a prefilter

[`func fetchPrefilter(existingPrefilterTag: String?) async throws -> NEURLFilterPrefilter?`](/documentation/NetworkExtension/NEURLFilterControlProvider/fetchPrefilter(existingPrefilterTag:))

Fetches prefilter data, in response to a call from the framework.

[`struct NEURLFilterPrefilter`](/documentation/NetworkExtension/NEURLFilterPrefilter)

A structure containing a prefilter returned by a filter control provider.

## Relationships

### Inherits From

[`AppExtension`](/documentation/ExtensionFoundation/AppExtension)

---

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