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# ReadableStream.cancel()

The **`cancel()`** method of the
`ReadableStream` interface returns a `Promise` that
resolves when the stream is canceled.

Cancel is used when you've completely finished with the stream and don't need any more
data from it, even if there are chunks enqueued waiting to be read. That data is lost
after cancel is called, and the stream is not readable any more. To read those chunks
still and not completely get rid of the stream, you'd use
`ReadableStreamDefaultController.close()`.

## Syntax

```js
cancel()
cancel(reason)
```

### Parameters

- `reason` _**optional**_
  - : A human-readable reason for the cancellation. The underlying source may or may not use it.

### Return value

A `Promise`, which fulfills with the value given in the `reason` parameter.

### Exceptions

- `TypeError`
  - : The stream you are trying to cancel is not a `ReadableStream`, or it is locked.
