A configuration object that defines behavior and policies for a URL session.


An URLSessionConfiguration 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.

It is important to configure your URLSessionConfiguration object appropriately before using it to initialize a session object. Session objects make a copy of the configuration settings you provide and use those settings to configure the session. Once configured, the session object ignores any changes you make to the URLSessionConfiguration object. If you need to modify your transfer policies, you must update the session configuration object and use it to create a new URLSession object.

For more information about using configuration objects to create sessions, see URLSession.


Creating a Session Configuration Object

class var `default`: URLSessionConfiguration

Returns a newly created default session configuration object.

class var ephemeral: URLSessionConfiguration

Returns a session configuration that uses no persistent storage for caches, cookies, or credentials.

class func background(withIdentifier: String)

Returns a session configuration object that allows HTTP and HTTPS uploads or downloads to be performed in the background.

Setting General Properties

var identifier: String?

The background session identifier of the configuration object.

var httpAdditionalHeaders: [AnyHashable : Any]?

A dictionary of additional headers to send with requests.

var allowsCellularAccess: Bool

A Boolean value that determines whether connections should be made over a cellular network.

var timeoutIntervalForRequest: TimeInterval

The timeout interval to use when waiting for additional data.

var timeoutIntervalForResource: TimeInterval

The maximum amount of time that a resource request should be allowed to take.

var sharedContainerIdentifier: String?

The identifier for the shared container into which files in background URL sessions should be downloaded.

Setting Cookie Policies

var httpCookieAcceptPolicy: HTTPCookie.AcceptPolicy

A policy constant that determines when cookies should be accepted.

var httpShouldSetCookies: Bool

A Boolean value that determines whether requests should contain cookies from the cookie store.

var httpCookieStorage: HTTPCookieStorage?

The cookie store for storing cookies within this session.

class HTTPCookieStorage

NSHTTPCookieStorage implements a singleton object (shared instance) that manages storage of cookies. Each cookie is represented by an instance of the HTTPCookie class. As a rule, cookies are shared among all applications and are kept in sync across process boundaries. Session cookies (where the cookie object’s isSessionOnly method returns true) are local to a single process and are not shared.

class HTTPCookie

An NSHTTPCookie object represents an HTTP cookie. It is an immutable object, initialized from a dictionary containing the cookie attributes.

Setting Security Policies

var tlsMaximumSupportedProtocol: SSLProtocol

The maximum TLS protocol version that the client should request when making connections in this session.

var tlsMinimumSupportedProtocol: SSLProtocol

The minimum TLS protocol that should be accepted during protocol negotiation.

var urlCredentialStorage: URLCredentialStorage?

A credential store that provides credentials for authentication.

Setting Caching Policies

var urlCache: URLCache?

The URL cache for providing cached responses to requests within the session.

var requestCachePolicy: NSURLRequest.CachePolicy

A predefined constant that determines when to return a response from the cache.

Supporting Background Transfers

var sessionSendsLaunchEvents: Bool

A Boolean value that indicates whether the app should be resumed or launched in the background when transfers finish.

var isDiscretionary: Bool

A Boolean value that determines whether background tasks can be scheduled at the discretion of the system for optimal performance.

Supporting Custom Protocols

var protocolClasses: [AnyClass]?

An array of extra protocol subclasses that handle requests in a session.

class URLProtocol

An NSURLProtocol object handles the loading of protocol-specific URL data. The NSURLProtocol class itself is an abstract class that provides the infrastructure for processing URLs with a specific URL scheme. You create subclasses for any custom protocols or URL schemes that your app supports.

Supporting Multipath TCP

var multipathServiceType: URLSessionConfiguration.MultipathServiceType

A service type that specifies the Multipath TCP connection policy for transmitting data over Wi-Fi and cellular interfaces.

enum URLSessionConfiguration.MultipathServiceType

Constants that specify the type of service that Multipath TCP uses.


Setting HTTP Policy and Proxy Properties

var httpMaximumConnectionsPerHost: Int

The maximum number of simultaneous connections to make to a given host.

var httpShouldUsePipelining: Bool

A Boolean value that determines whether the session should use HTTP pipelining.

var connectionProxyDictionary: [AnyHashable : Any]?

A dictionary containing information about the proxy to use within this session.

Deprecated Methods

class func backgroundSessionConfiguration(String)

Returns a session configuration object that allows HTTP and HTTPS uploads or downloads to be performed in the background.


Instance Properties


Inherits From

See Also

First Steps

class URLSession

An object that coordinates a group of related network data transfer tasks.

class URLSessionTask

A task, such as downloading a specific resource, to be undertaken by a URL session.

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