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# increaseLength(by:)

Increases the length of the receiver by a given number of bytes.

```
func increaseLength(by extraLength: Int)
```

## Parameters

`extraLength`

The number of bytes by which to increase the receiver’s length.

## Discussion

The additional bytes are all set to `0`.

> Important:
> Changing the length of a mutable data object invalidates any existing data pointers returned by the ``doc://com.apple.foundation/documentation/Foundation/NSData/bytes`` or ``doc://com.apple.foundation/documentation/Foundation/NSMutableData/mutableBytes`` properties.

## See Also

[`length`](/documentation/Foundation/NSMutableData/length)

The number of bytes contained in the mutable data object.


---

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