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# JSONEncoder.KeyEncodingStrategy

The values that determine how to encode a type’s coding keys as JSON keys.

```
enum KeyEncodingStrategy
```

## Overview> Note:
> Key encoding strategies other than ``doc://com.apple.foundation/documentation/Foundation/JSONEncoder/KeyEncodingStrategy-swift.enum/useDefaultKeys`` may have a noticeable performance cost because those strategies may inspect and transform each key.

## Topics

### Built-in Encoding

[`JSONEncoder.KeyEncodingStrategy.convertToSnakeCase`](/documentation/Foundation/JSONEncoder/KeyEncodingStrategy-swift.enum/convertToSnakeCase)

A key encoding strategy that converts camel-case keys to snake-case keys.

[`JSONEncoder.KeyEncodingStrategy.useDefaultKeys`](/documentation/Foundation/JSONEncoder/KeyEncodingStrategy-swift.enum/useDefaultKeys)

A key encoding strategy that doesn’t change key names during encoding.

### Custom Encoding

[`JSONEncoder.KeyEncodingStrategy.custom(_:)`](/documentation/Foundation/JSONEncoder/KeyEncodingStrategy-swift.enum/custom(_:))

A key encoding strategy defined by the closure you supply.


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