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# startFilter(completionHandler:)

Start the filter.

```
func startFilter(completionHandler: @escaping @Sendable ((any Error)?) -> Void)
```

## Parameters

`completionHandler`

A block that must be executed when the filter is running and is ready to filter network content.

## Discussion

This method is called by the system to start the filter.

`NEFilterProvider` subclasses must override this method.

When this method is called, the Filter Provider should perform any steps necessary to initialize the filter and then execute the `completionHandler` block.

---

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