# IAM JSON policy elements: Supported data types
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This section lists the data types that are supported when you specify values in JSON policies. The policy language doesn't support all types for each policy element; for information about each element, see the preceding sections.
+ Strings
+ Numbers (Ints and Floats)
+ Boolean
+ Null
+ Lists
+ Maps
+ Structs (which are just nested Maps)

The following table maps each data type to the serialization. Note that all policies must be in UTF-8. For information about the JSON data types, go to [RFC 4627](https://datatracker.ietf.org/doc/html/rfc4627).


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| Type | JSON | 
| --- | --- | 
|  String  |  String  | 
|  Integer  |  Number  | 
|  Float  |  Number  | 
|  Boolean  |  true false  | 
|  Null  |  null  | 
|  Date  |  String adhering to the [W3C Profile of ISO 8601](http://www.w3.org/TR/NOTE-datetime)  | 
|  IpAddress  |  String adhering to [RFC 4632](https://datatracker.ietf.org/doc/html/rfc4632)  | 
|  List  |  Array  | 
|  Object  |  Object  |