# connection(_:willCacheResponse:) Sent before the connection stores a cached response in the cache, to give the delegate an opportunity to alter it. ``` optional func connection(_ connection: NSURLConnection, willCacheResponse cachedResponse: CachedURLResponse) -> CachedURLResponse? ``` ## Parameters `connection` The connection sending the message. `cachedResponse` The proposed cached response to store in the cache. ## Return Value The actual cached response to store in the cache. The delegate may return `cachedResponse` unmodified, return a modified cached response, or return `nil` if no cached response should be stored for the connection. ## Discussion This method is called only if the [`URLProtocol`](/documentation/Foundation/URLProtocol) handling the request decides to cache the response. As a rule, responses are cached only when all of the following are true: - The request is for an HTTP or HTTPS URL (or your own custom networking protocol that supports caching). - The request was successful (with a status code in the `200–299` range). - The provided response came from the server, rather than out of the cache. - The [`NSURLRequest`](/documentation/Foundation/NSURLRequest) object’s cache policy allows caching. - The cache-related headers in the server’s response (if present) allow caching. - The response size is small enough to reasonably fit within the cache. (For example, if you provide a disk cache, the response must be no larger than about 5% of the disk cache size.) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)