# Checking Volume Storage Capacity Confirm that you have enough local storage space for a large amount of data. ## Discussion Before you try to store a large amount of data locally, first verify that you have sufficient storage capacity. To get the storage capacity of a volume, you construct a URL (using an instance of [`URL`](/documentation/Foundation/URL)) that references an object on the volume to be queried, and then query that volume. ### Decide Which Query Type to Use The query type to use depends on what’s being stored. If you’re storing data based on a user request or resources the app requires to function properly (for example, a video the user is about to watch or resources that are needed for the next level in a game), query against [`volumeAvailableCapacityForImportantUsageKey`](/documentation/Foundation/URLResourceKey/volumeAvailableCapacityForImportantUsageKey). However, if you’re downloading data in a more predictive manner (for example, downloading a newly available episode of a TV series that the user has been watching recently), query against [`volumeAvailableCapacityForOpportunisticUsageKey`](/documentation/Foundation/URLResourceKey/volumeAvailableCapacityForOpportunisticUsageKey). ### Construct a Query Use this example as a guide to construct your own query: ```objc NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:@"/"]; NSError *error = nil; NSDictionary *results = [fileURL resourceValuesForKeys:@[NSURLVolumeAvailableCapacityForImportantUsageKey] error:&error]; if (!results) { NSLog(@"Error retrieving resource keys: %@\n%@", [error localizedDescription], [error userInfo]); abort(); } NSLog(@"Available capacity for important usage: %@", results[NSURLVolumeAvailableCapacityForImportantUsageKey]); ``` --- 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)