Format, minify, sort keys, explore with tree view, run JSONPath queries, generate mock data, and share — all client-side.
Indent:
1
Output
Understanding JSON: A Developer's Guide
JSON (JavaScript Object Notation) is the dominant data interchange format on the web. This tool provides everything you need to work with JSON efficiently: formatting, validation with precise line/column error pinpointing, an interactive tree view for navigating complex structures, JSONPath querying, and the ability to share and generate mock data — all without sending your data to a server.
Common JSON Errors
Trailing commas after the last item in an object or array are the #1 mistake. Unquoted keys are another — JSON requires double quotes around all keys, unlike JavaScript. Single quotes are invalid; only double quotes " are allowed. This tool pinpoints the exact line and column of every error.
JSON vs XML
JSON is typically 30-50% smaller than equivalent XML and significantly faster to parse. XML supports namespaces, comments, and schemas, making it better for complex document-type data. For web APIs, microservices, and configuration files, JSON is the standard choice.
Why Format JSON?
Raw API responses or minified JSON are single continuous lines. Formatting adds indentation and line breaks, making nested structures visible at a glance. This dramatically speeds up debugging — you can immediately see missing fields, wrong types, or unexpected null values.
JSONPath Querying
JSONPath lets you extract specific values from complex JSON. Use $ for root, .key for children, [0] for array elements, [*] for all items, and .. for recursive descent. Example: $..price finds every "price" at any depth.
Mock Data Generation
The Mock Data feature analyzes your JSON structure and generates randomized but structurally identical data. It uses heuristics to produce realistic values — emails stay as emails, dates as dates, names as names. This is ideal for creating test fixtures, populating development databases, or sharing API response shapes without exposing real data.
About JSON Formatter
JSON is the default serialization format for APIs, config files, and logs. A minified payload from a server is unreadable; a hand-written one is usually broken. A formatter re-indents the structure so you can scan it, and a validator points at the exact character where parsing failed. This tool does both, and adds a collapsible tree view so you can drill into deeply nested objects without scrolling.
What this tool does
Format — re-indent JSON with 2 or 4 spaces, or tabs.
Minify — collapse to a single line for transport.
Validate — strict RFC 8259 parsing with line/column error pointers.
Tree view — collapsible nodes, type badges, copy-path on each key.
JSONPath — query with expressions like $.users[*].name.
Common errors and how to fix them
Trailing commas after the last array or object element will trip the parser; remove them. Keys must be wrapped in double quotes — single quotes are JavaScript literals, not JSON. Comments (// or /* */) are not part of the spec and must be stripped before parsing. Unescaped control characters inside strings (raw newlines, tabs) need to be replaced with their escape sequences (\n, \t). When the message says Unexpected tokenwith a position, the offending character is at that exact byte offset; jump there and the issue is usually obvious.
JSON to YAML — convert config payloads bidirectionally.
Text Diff — compare two formatted documents side-by-side.
Privacy
Your JSON stays in your browser. No analytics, no logging, no upload. The optional History panel writes to IndexedDB on your device only. Read our privacy policy.
Frequently asked
Is my JSON sent to a server?
No. Parsing, formatting, and validation all run in your browser. Nothing is uploaded, logged, or transmitted.
How big a document can it handle?
Documents up to ~5 MB format smoothly on a typical laptop. Beyond that the worker still parses but the tree view may pause briefly while rendering. Very large arrays are virtualized.
Why does my JSON fail to parse?
The most common culprits are trailing commas, single quotes around keys or strings, unquoted keys, and stray comments. Standard JSON allows none of those. The error pointer shows the line and column of the first invalid character.
What is the difference between JSON and JSON5?
JSON5 is a superset that allows comments, trailing commas, single quotes, and unquoted keys. This formatter targets strict JSON (RFC 8259). If you need JSON5, convert to strict JSON first.