JSON Formatter

Format and pretty-print JSON data with customizable indentation.

Indent

JSON Input

Output

Formatted JSON will appear here…

Share This Tool

What Is JSON?

JSON (JavaScript Object Notation) is a lightweight data interchange format used by virtually every web API, configuration file, database, and modern application. It stores structured data as human-readable text using key-value pairs, arrays, strings, numbers, booleans, and null values. Despite its name, JSON is language-agnostic and supported natively in Python, Java, PHP, Ruby, Go, and hundreds of other languages.

Why Format JSON?

APIs and databases typically transmit JSON as a minified single line to reduce payload size. While efficient for machines, minified JSON is nearly impossible for humans to read or debug. A 50-field API response compressed to one line forces developers to mentally parse nested brackets and commas. Formatting (or "pretty-printing") adds structured indentation that reveals the data hierarchy at a glance.

Common Situations Where You Need a JSON Formatter

API debugging — Paste a raw API response to understand its structure before writing code to parse it
Config file editing — Read and edit package.json, tsconfig.json, or settings.json without a code editor
Database inspection — Format JSON stored in database columns (PostgreSQL JSONB, MongoDB documents)
Log analysis — Make structured log entries readable for incident investigation
Code review — Share formatted JSON with teammates instead of minified strings
Minification — Strip whitespace from JSON config files before committing to reduce repository size

Format vs Minify vs Validate

Format (Pretty-print) adds indentation and line breaks to make JSON readable. Choose 2-space indentation for compact readability or 4-space for maximum clarity. Minify removes all unnecessary whitespace to produce the smallest possible JSON string — useful for API payloads and performance optimization. Validate checks whether your JSON is syntactically correct without transforming it, and shows you a summary of the top-level structure.

Understanding JSON Errors

The most common JSON errors are: trailing commas after the last element (valid in JavaScript but not in JSON), single quotes instead of double quotes for strings, unquoted property keys, and missing commas between elements. When validation fails, this tool shows the exact error message from the browser's JSON parser, pointing you to the problematic syntax.

Privacy

All JSON processing is done entirely in your browser using the native JSON.parse() and JSON.stringify() functions. Your data — including any API keys, tokens, or sensitive values inside your JSON — never leaves your device.

Frequently Asked Questions

What is the difference between 2-space and 4-space indentation?

2-space indentation produces more compact output that fits more data on screen, making it popular for web development. 4-space indentation provides more visual separation and is preferred in environments like Python development and some corporate style guides. Both are completely valid JSON — the indentation choice is purely cosmetic and has no effect on how the JSON is parsed.

Why is my JSON showing an error even though it looks correct?

The most common causes are: (1) trailing commas after the last property or array item — JSON strictly forbids this unlike JavaScript, (2) single-quoted strings — JSON requires double quotes only, (3) unquoted keys — all keys must be in double quotes, and (4) comments — JSON does not support // or /* */ comments. Remove any of these elements and try again.

Can I format very large JSON files?

This tool handles large JSON in your browser memory. Modern browsers can typically handle files up to 50–100 MB in a text field, though performance may slow with very large files. For JSON files larger than 10 MB, a desktop tool like VS Code with the Prettier extension or jq in the command line will perform better.

What does the Validate mode tell me?

Validate mode parses your JSON and confirms it is syntactically valid, then shows you the top-level data type (object or array) and lists the top-level keys or array item count. This is useful for quickly understanding the shape of an unfamiliar API response before writing parsing code.

Can I format JSON5 or JSONC (JSON with Comments)?

No. This tool strictly follows the JSON specification (RFC 8259). JSON5 and JSONC are supersets of JSON that add comments and trailing commas — they require specialized parsers. If you have JSONC (common in VS Code settings files), remove the comments first, then format with this tool.

Is my JSON data private?

Yes. All processing runs locally in your browser using native JavaScript. No JSON content is transmitted to any server. This is important for JSON that may contain API keys, access tokens, database credentials, or personal user data — all of which stay entirely on your device.

How is this different from JSON formatting in VS Code?

Functionally they produce the same result. This tool is faster to access when you just need to quickly format a response — open browser, paste, done. VS Code requires opening the editor, creating a file, and running a format command. For quick one-off formatting tasks, a browser tool is simply more convenient.

Is it free?

Completely free with no sign-up or installation. Works in any modern browser. All JSON parsing and formatting uses native browser APIs — no external libraries are loaded.