Free JSON Formatter and Validator Online

A JSON formatter takes raw, minified, or malformed JSON and restructures it into clean, properly indented, human-readable output. JSON (JavaScript Object Notation) is the universal data format for REST APIs, configuration files, and web applications, but API responses and log files are almost always minified and unreadable without a formatter.

This free online JSON formatter goes beyond pretty-printing: it validates syntax, shows a collapsible tree view, compares two JSON documents, and supports JSONC (JSON with comments).

How to format JSON online

Paste your raw or minified JSON into the input panel.
Click Format to beautify and validate instantly.
Use the tree view to collapse and expand nested objects and arrays.
Switch to the Diff tab to compare two JSON documents side by side.
Copy the formatted output or download it as a file.

JSON validation: common errors explained

Trailing comma: {"key": "value",} is invalid in JSON (valid in JSONC). The formatter highlights the exact line.
Single quotes: JSON requires double quotes for strings. Single quotes cause a parse error.
Unquoted keys: Unlike JavaScript objects, JSON keys must always be quoted strings.
Comments: Standard JSON does not support comments. Use the JSONC mode to handle // line and /* block */ comments.

Beautify vs Minify JSON

Beautify: Adds indentation and line breaks for readability. Use during development, debugging, and code review.
Minify: Removes all whitespace and optional formatting to reduce payload size. Use for API responses, localStorage data, and production configs.

JSON diff and schema validation

The built-in diff tool highlights added, removed, and changed keys between two JSON documents: useful for comparing API response versions, config snapshots, or migration output. The JSON Schema validator checks that your data matches a defined structure and reports missing required fields, wrong types, and enum violations.

JSON Formatter