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# JSONSerialization

An object that converts between JSON and the equivalent Foundation objects.

```
class JSONSerialization
```

## Overview

You use the [`JSONSerialization`](/documentation/Foundation/JSONSerialization) class to convert JSON to Foundation objects and convert Foundation objects to JSON.

To convert a Foundation object to JSON, the object must have the following properties:

- The top level object is an [`NSArray`](/documentation/Foundation/NSArray) or [`NSDictionary`](/documentation/Foundation/NSDictionary), unless you set the [`fragmentsAllowed`](/documentation/Foundation/JSONSerialization/WritingOptions/fragmentsAllowed) option.
- All objects are instances of [`NSString`](/documentation/Foundation/NSString), [`NSNumber`](/documentation/Foundation/NSNumber), [`NSArray`](/documentation/Foundation/NSArray), [`NSDictionary`](/documentation/Foundation/NSDictionary), or [`NSNull`](/documentation/Foundation/NSNull).
- All dictionary keys are instances of [`NSString`](/documentation/Foundation/NSString).
- Numbers are neither `NaN` nor infinity.

Other rules may apply. Calling [`isValidJSONObject(_:)`](/documentation/Foundation/JSONSerialization/isValidJSONObject(_:)) or attempting a conversion are the definitive ways to tell if the [`JSONSerialization`](/documentation/Foundation/JSONSerialization) class can convert given object to JSON data.

> Note:
> On iOS 7 and later and macOS 10.9 and later, ``doc://com.apple.foundation/documentation/Foundation/JSONSerialization`` is thread safe.

## Topics

### Creating a JSON Object

[`jsonObject(with:options:)`](/documentation/Foundation/JSONSerialization/jsonObject(with:options:)-8demi)

Returns a Foundation object from given JSON data.

[`jsonObject(with:options:)`](/documentation/Foundation/JSONSerialization/jsonObject(with:options:)-3afap)

Returns a Foundation object from JSON data in a given stream.

[`JSONSerialization.ReadingOptions`](/documentation/Foundation/JSONSerialization/ReadingOptions)

Options used when creating Foundation objects from JSON data.

### Creating JSON Data

[`data(withJSONObject:options:)`](/documentation/Foundation/JSONSerialization/data(withJSONObject:options:))

Returns JSON data from a Foundation object.

[`writeJSONObject(_:to:options:error:)`](/documentation/Foundation/JSONSerialization/writeJSONObject(_:to:options:error:))

Writes a given JSON object to a stream.

[`JSONSerialization.WritingOptions`](/documentation/Foundation/JSONSerialization/WritingOptions)

Options for writing JSON data.

[`isValidJSONObject(_:)`](/documentation/Foundation/JSONSerialization/isValidJSONObject(_:))

Returns a Boolean value that indicates whether the serializer can convert a given object to JSON data.


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