<!--
{
  "availability" : [
    "macOS: -"
  ],
  "documentType" : "symbol",
  "framework" : "FSKit",
  "identifier" : "/documentation/FSKit/FSFileSystem",
  "metadataVersion" : "0.1.0",
  "role" : "Class",
  "symbol" : {
    "kind" : "Class",
    "modules" : [
      "FSKit"
    ],
    "preciseIdentifier" : "c:objc(cs)FSFileSystem"
  },
  "title" : "FSFileSystem"
}
-->

# FSFileSystem

An abstract base class for implementing a full-featured file system.

```
@interface FSFileSystem : NSObject
```

## Overview

`FSFileSystem` is a full-featured file system, which works with one or more [`FSResource`](/documentation/FSKit/FSResource) instances and presents one or more [`FSVolume`](/documentation/FSKit/FSVolume) references to callers.

Implement your app extension by providing a subclass of `FSFileSystem` as a delegate object.
Your delegate also needs to implement the `FSFileSystemOperations` protocol so that it can probe, load, and unload resources.

> Note: The current version of FSKit supports only ``doc://FSKit/documentation/FSKit/FSUnaryFileSystem``, not `FSFileSystem`.

---

Copyright &copy; 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)