JSON Formatter
Format, minify, and validate JSON with syntax highlighting
Input
Output
What Is a JSON Formatter?
JSON (JavaScript Object Notation) is the most widely used data format on the web today. APIs return it, config files use it, databases store it. The JSON specification keeps things minimal, which is great for machines but not so great when you need to actually read the data. A JSON formatter adds indentation and line breaks to raw or minified JSON so you can see the structure clearly.
This tool runs entirely in your browser. Your JSON goes through JSON.stringify() with 2-space indentation, and the result shows up in the output panel. Nothing is sent to a server, so it's safe to use with production data, tokens, or anything else you wouldn't want leaving your machine.
JSON Formatting Examples
Here are some examples of what the formatter does. Minified or compact JSON is hard to read; formatting it reveals the structure at a glance.
Example 1: Subscriber record
Minified input (single line):
Formatted output:
Example 2: Call records
Minified input:
Formatted output:
Click the Sample button above to load a ready-made example (mobile plan data) into the editor and see the formatter in action.
How to Use This Tool
Paste or Upload
Copy your JSON and paste it into the left editor. You can also click Upload to load a .json or .txt file from your computer. The Sample button loads example data if you want to test things out.
Check the Output
The right panel updates automatically as you type. Valid JSON gets formatted with proper indentation following RFC 8259. If there's a syntax error (missing bracket, trailing comma, unquoted key), you'll see an error message instead.
Copy, Download, or Minify
Use Copy to put the result on your clipboard, Download to save it as a file, or Minify to remove all whitespace and get a compact single-line version.
How the Formatter Works
Both editors use Ace Editor, which provides syntax highlighting, line numbers, and JSON-specific error markers. When you paste or type JSON in the input panel, the tool waits 300ms (to avoid parsing mid-keystroke), then runs JSON.parse() on your input. If parsing succeeds, it calls JSON.stringify(data, null, 2) and displays the result. If parsing fails, the output shows an error.
Worth noting: JSON does not support comments. That's defined in the spec itself, not a limitation of this tool. Files like VS Code's settings.json use JSONC (JSON with Comments), which is a different format. If your file has comments, you'll need to remove them before formatting.
Where JSON Formatting Helps
Most developers end up needing a formatter when they're reading API responses. You send a request through Postman or curl, and the response comes back as a single compressed line. Pasting it here makes nested objects and arrays visible immediately. For pulling out specific values from large responses, the JSON Path tool works well alongside this.
Config files are another common case. A package.json or tsconfig.json with inconsistent indentation is hard to review in a pull request. Formatting it here gives you a consistent version you can paste back. If you need to combine two config files, there's a separate JSON Merge tool for that.
Database exports from MongoDB, Firestore, or CouchDB are typically large JSON blobs with no formatting. Running them through here helps you understand the document structure before writing import scripts or queries. If you need the data in a spreadsheet instead, you can use JSON to CSV to convert it.
It's also useful before sharing JSON with teammates. Formatted JSON in a Slack message or a Jira ticket is much easier to read than a raw minified string. Running it through the JSON Validator first can catch issues before anyone else sees them.
Frequently Asked Questions
Is my data private?
Yes. The formatting happens in your browser using JavaScript. No data is sent to any server. You can confirm this by opening your browser's Network tab while using the tool.
What's the size limit?
There's no hard limit from the tool itself. It depends on your browser's available memory. JSON files up to 10-15 MB generally work without issues in Chrome and Firefox. For very large files (hundreds of MBs), a command-line tool like jq is more practical.
What does Minify do?
It removes all whitespace (newlines, spaces, indentation) from the formatted output, giving you the smallest possible version of the JSON. This is useful for embedding JSON in URLs, storing it in database fields, or reducing payload size over the network. There's also a dedicated JSON Minifier page.
Why does the output say "Invalid JSON"?
The input has a syntax error. Common causes include trailing commas after the last element, single quotes instead of double quotes, unquoted property names, or mismatched brackets. The JSON spec is strict about all of these.
Can this validate JSON against a schema?
This tool validates syntax (whether the JSON is well-formed), not structure. For schema validation, use the JSON Schema Generator to generate a schema from sample data, or the JSON Validator for more detailed checks.
Related Tools
For a deeper look at JSON as a format, MDN's JSON guide covers parsing, stringifying, and common pitfalls. The formal standard is RFC 8259 if you need the full technical reference.