# Errors and Exceptions Respond to problem situations in your interactions with APIs, and fine-tune your app for better debugging. ## Topics ### User-Relevant Errors [`NSError`](/documentation/Foundation/NSError) Information about an error condition including a domain, a domain-specific error code, and application-specific information. [`LocalizedError`](/documentation/Foundation/LocalizedError) A specialized error that provides localized messages describing the error and why it occurred. [`RecoverableError`](/documentation/Foundation/RecoverableError) A specialized error that may be recoverable by presenting several potential recovery options to the user. [`CustomNSError`](/documentation/Foundation/CustomNSError) A specialized error that provides a domain, error code, and user-info dictionary. ### Assertions [`NSAssertionHandler`](/documentation/Foundation/NSAssertionHandler) An object that logs an assertion to the console. [`NSAssert`](/documentation/Foundation/NSAssert) Generates an assertion if a given condition is false. [`NSAssert1`](/documentation/Foundation/NSAssert1) Generates an assertion if a given condition is false. [`NSAssert2`](/documentation/Foundation/NSAssert2) Generates an assertion if a given condition is false. [`NSAssert3`](/documentation/Foundation/NSAssert3) Generates an assertion if a given condition is false. [`NSAssert4`](/documentation/Foundation/NSAssert4) Generates an assertion if a given condition is false. [`NSAssert5`](/documentation/Foundation/NSAssert5) Generates an assertion if a given condition is false. [`NSCAssert`](/documentation/Foundation/NSCAssert) Generates an assertion if the given condition is false. [`NSCAssert1`](/documentation/Foundation/NSCAssert1) Generates an assertion if a given condition is false. [`NSCAssert2`](/documentation/Foundation/NSCAssert2) Generates an assertion if a given condition is false. [`NSCAssert3`](/documentation/Foundation/NSCAssert3) Generates an assertion if a given condition is false. [`NSCAssert4`](/documentation/Foundation/NSCAssert4) Generates an assertion if a given condition is false. [`NSCAssert5`](/documentation/Foundation/NSCAssert5) Generates an assertion if a given condition is false. [`NSCParameterAssert`](/documentation/Foundation/NSCParameterAssert) Evaluates the specified parameter. [`NSParameterAssert`](/documentation/Foundation/NSParameterAssert) Validates the specified parameter. ### Exceptions [`NSException`](/documentation/Foundation/NSException) An object that represents a special condition that interrupts the normal flow of program execution. ### Diagnostics and Debugging [`NSLog`](/documentation/Foundation/NSLog) Logs an error message to the Apple System Log facility. [`NSLogv(_:_:)`](/documentation/Foundation/NSLogv(_:_:)) Logs an error message to the Apple System Log facility. [`NSLog(_:_:)`](/documentation/Foundation/NSLog(_:_:)) Logs an error message to the Apple System Log facility. [`NSDeallocateZombies`](/documentation/Foundation/NSDeallocateZombies) A global variable that determines whether or not the memory of zombie objects is deallocated. [`NSDebugEnabled`](/documentation/Foundation/NSDebugEnabled) A global variable that can be used to enable debug behavior in your app, such as extra logging. [`NSZombieEnabled`](/documentation/Foundation/NSZombieEnabled) A global variable related to zombie objects that in practice has no effect. [`NSKeepAllocationStatistics`](/documentation/Foundation/NSKeepAllocationStatistics) A no-longer-used global variable related to keeping statistics. --- 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)