JSON Validator & Formatter
Validate, format, minify, and visualize JSON in an interactive tree view.
What Is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format that has become the de facto standard for APIs, configuration files, and data storage across the web. Originally derived from JavaScript, JSON is language-independent and supported natively by virtually every modern programming language.
A JSON document consists of two fundamental structures: objects (key-value pairs enclosed in curly braces) and arrays (ordered lists enclosed in square brackets). Values can be strings, numbers, booleans, null, or nested objects and arrays. This simplicity, combined with its readability, makes JSON the preferred format for REST APIs, NoSQL databases like MongoDB and Firebase, and front-end/back-end communication.
Despite its simplicity, invalid JSON is a common source of bugs. Missing commas, trailing commas, unquoted keys, and mismatched brackets are frequent issues. A JSON validator and formatter like this tool helps developers quickly identify syntax errors, visualize nested data structures, and produce clean, properly indented output.
How to Use This JSON Formatter
Our JSON Formatter provides three output modes: an interactive tree view, formatted (pretty-printed) output, and minified output. Here’s how to use each:
- Paste or Upload — Paste your JSON string into the input area, or upload a
.jsonfile from your device. - Validate & Format — Click the button or press Ctrl+Enter. If the JSON is valid, you’ll see a green confirmation and the parsed output.
- Switch Views — Use the “Tree / Formatted / Minified” tabs to toggle between an interactive collapsible tree, pretty-printed JSON with 2-space indentation, or a compact single-line minified version.
- Copy Output — Click “Copy” to copy the current output view to your clipboard.
Everything runs client-side in your browser. Your JSON data is never uploaded to any server. Free users can process up to 100KB; Pro users have no limit.
Frequently Asked Questions
Can I validate JSON with comments?
Standard JSON (RFC 8259) does not support comments. If your JSON contains // or /* */ comments, they must be removed before validation. Some formats like JSONC or JSON5 support comments, but they are not standard JSON and require dedicated parsers.
What's the difference between formatted and minified JSON?
Formatted (pretty-printed) JSON uses indentation and newlines for human readability. Minified JSON removes all whitespace to reduce file size — useful for production APIs and network transfers where every byte matters. Minification typically reduces JSON size by 20-40%.
Is my data sent to a server for processing?
No. All JSON parsing, formatting, and minification happens entirely in your browser using the native JSON.parse() and JSON.stringify() APIs. Your data never leaves your device.
What causes 'Unexpected token' errors?
Common causes include: trailing commas after the last element in an object or array (e.g., {"a": 1,}), single-quoted strings instead of double-quoted, unquoted property names, and missing commas between elements. Our validator highlights the exact character position of the error.
What is the maximum JSON file size this tool supports?
Free users can process JSON files up to 100KB. Pro subscribers can process files of any size, including large API responses, database exports, and multi-megabyte configuration files.
Can JSON represent all data types?
JSON supports strings, numbers, booleans, null, arrays, and objects. It does not natively support dates, binary data, undefined, functions, or circular references. Dates are typically represented as ISO 8601 strings. Binary data must be Base64-encoded. These limitations are by design to keep JSON simple and universally parseable.
What is JSON Schema and how does it differ from JSON validation?
JSON validation checks that a string is syntactically valid JSON. JSON Schema (jsonschema.org) goes further — it defines the expected structure, required fields, data types, and value constraints. Our tool performs syntax validation; Schema validation requires a separate tool or library (like Ajv for JavaScript).
Is JSON better than XML for API data exchange?
For most REST APIs, yes. JSON is more compact, easier to parse in JavaScript, and better aligned with object-oriented data models. However, XML has advantages for document-centric data, namespaces, mixed content, and formal schema validation (XSD). German e-invoicing (XRechnung) uses XML precisely because of these strengths.
How do I handle special characters in JSON strings?
JSON strings must use double quotes and escape certain characters: forward slash (/), backslash (\\), double quote (\"), and control characters. Unicode characters outside ASCII should be escaped as \uXXXX (e.g., \u00e9 for é). Our formatter automatically escapes or preserves these characters correctly.