# assumesTopLevelDictionary Specifies that decoding assumes the top level of the JSON data is a dictionary, even if it doesn’t begin and end with braces. ``` var assumesTopLevelDictionary: Bool { get set } ``` ## Discussion This is an extension to JSON5 that’s not part of the specification. [`AttributedString`](/documentation/Foundation/AttributedString) uses this option, along with [`allowsJSON5`](/documentation/Foundation/JSONDecoder/allowsJSON5), to support the use of JSON5 inside Markdown strings that use multiple custom attributes. Using [`assumesTopLevelDictionary`](/documentation/Foundation/JSONDecoder/assumesTopLevelDictionary) allows for the following syntax inside the parentheses of the custom attribute markup: ```swift This is a [Markdown](https://commonmark.org) string with a ^[custom attribute](factor: 10, other: true). ``` Without [`assumesTopLevelDictionary`](/documentation/Foundation/JSONDecoder/assumesTopLevelDictionary), the markup would have to use explicit enclosing braces to declare the contents of the parentheses to be a dictionary: ```swift This is a [Markdown](https://commonmark.org) string with a ^[custom attribute]({factor: 10, other: true}). ``` When you use braces, you must use matched pairs. This means that with [`assumesTopLevelDictionary`](/documentation/Foundation/JSONDecoder/assumesTopLevelDictionary) set, the syntax `({…})` and `(…)` are both legal, but `({…)` and `(…})` are not. --- 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)