---
title: URL Loading System error info keys
framework: foundation
role: collectionGroup
role_heading: API Collection
path: foundation/url-loading-system-error-info-keys
---

# URL Loading System error info keys

Recognize these keys from the user info dictionary of error objects produced by URL Loading APIs.

## Overview

Overview These keys are only present in the NSURLErrorDomain.

## Topics

### Keys

- [NSURLErrorFailingURLErrorKey](foundation/nsurlerrorfailingurlerrorkey.md)
- [NSURLErrorFailingURLPeerTrustErrorKey](foundation/nsurlerrorfailingurlpeertrusterrorkey.md)
- [NSURLErrorFailingURLStringErrorKey](foundation/nsurlerrorfailingurlstringerrorkey.md)
- [NSURLErrorBackgroundTaskCancelledReasonKey](foundation/nsurlerrorbackgroundtaskcancelledreasonkey.md)
- [URL Session Background Task Cancellation Reasons](foundation/url-session-background-task-cancellation-reasons.md)
- [NSURLErrorNetworkUnavailableReasonKey](foundation/nsurlerrornetworkunavailablereasonkey.md)
- [URLError.NetworkUnavailableReason](foundation/urlerror/networkunavailablereason-swift.enum.md)

### Deprecated

- [NSErrorFailingURLStringKey](foundation/nserrorfailingurlstringkey.md)

## See Also

### Errors

- [URLError](foundation/urlerror.md)