edn

Extensible Data Notation (EDN) is a data notation designed for use with Clojure and its ecosystem. Created by Rich Hickey, EDN serves as a portable, human- and machine-readable format for representing data structures, with a focus on being simple yet extensible enough to carry richer types than JSON allows. EDN is a subset of Clojure data structures and is intended to be usable outside of the Clojure compiler.

Syntax and data types: EDN uses tokens to represent literals such as nil, true, false; numbers, strings; and symbols and keywords. It supports standard collections: lists (), vectors [], maps {}, and sets #{}. Keys in maps can be keywords (e.g., :name), strings, or symbols. It also supports tagged literals to represent types like dates or UUIDs, for example #inst "2023-01-01T00:00:00Z" or #uuid "123e4567-e89b-12d3-a456-426614174000". Numbers can be integers, floats, and ratios; strings support standard escaping.

Usage: EDN is used for data interchange between programs in the Clojure ecosystem and beyond. Tools exist in Java, Python, JavaScript, and other languages to read and write EDN. Tagged literals enable custom data semantics while remaining a plain data format when tags are not processed.

Relation to JSON and scope: Compared with JSON, EDN offers richer literals and a syntax that aligns with Clojure data structures, at the cost of broader cross-language support. It is widely used in configuration, data exchange, and tooling within Clojure projects, and is governed by a formal specification.

See also: Clojure, JSON, data notation, tagged literals, EDN libraries.