# Modules.URLSession.SessionConfiguration
The session configuration object used to create new url sessions.
# Overview
These APIs are supported on iOS 7 and later.
An NSURLSessionConfiguration object defines the behavior and policies to use when uploading and downloading data using an URLSession object. When uploading or downloading data, creating a configuration object is always the first step you must take. You use this object to configure the timeout values, caching policies, connection requirements, and other types of information that you intend to use with your URLSession object.
iOS Background Services guide (opens new window).
# Properties
# HTTPHeaderFields
Specifies additional headers which will be set on outgoing requests. Keys and values must be Strings.
# identifier CREATION ONLY
The unique identifier for the configuration object.
This parameter must not be non-null or an empty string.