JSONn

JSONn is a proposed extension of the JavaScript Object Notation (JSON) data-interchange format intended to address common developer needs such as comments, trailing commas, and relaxed quoting rules while retaining JSON compatibility where possible. The name evokes JSON with "n" standing for "notes" or "next," reflecting its focus on readability and minor syntactic relaxations rather than a wholesale replacement of JSON.

The core ideas behind JSONn include support for inline and block comments, optional quotes around object keys that are valid identifiers, allowance of trailing commas in arrays and objects, and a more permissive string literal syntax (including multi-line strings and common escape sequences). JSONn aims for a superset relationship so valid JSON remains valid JSONn; however, JSONn features typically require dedicated parsers or preprocessing to convert to strict JSON for systems that demand it.

Adoption and tooling for JSONn vary by ecosystem. Some projects and libraries offer parsers or transpilers that convert JSONn to standard JSON, often used for configuration files, documentation snippets, and settings where human editing is frequent. JSONn is frequently compared to formats like JSON5, JSON with Comments (JSONC), and YAML — each balances human-friendliness and machine strictness differently.

Criticisms of JSONn focus on fragmentation of the JSON ecosystem, potential ambiguity introduced by relaxed syntax, and the need for extra processing steps. Proponents argue the format improves developer ergonomics without abandoning the simplicity and ubiquity of JSON.