Free developer tool

JSON Formatter & Validator

Format, validate, minify, and inspect JSON directly in your browser. Paste raw JSON or upload a file — see errors instantly, view structure stats, and copy clean output. No account or upload required.

Free to useNo account, no signup, no credit card.

Private by designRuns entirely in your browser. Nothing is uploaded.

Instant validationSee exact parser errors as you type.

Paste JSON to format, validate, and inspect

Validate, format, and minify JSON. Upload a file or paste raw JSON. All processing happens in your browser.

📁 Upload JSON file

Indent:

Input JSON

Formatted Output

Waiting for valid JSON...

Privacy note: This tool runs entirely in your browser. No JSON data is uploaded, stored, or transmitted. Paste sensitive or proprietary JSON with confidence.

Private by design

This tool uses your browser's native JSON parser. No data leaves your device — you can safely paste API responses, config files, or proprietary JSON without worrying about data exposure.

How to use this tool

Paste your JSON into the input area, or upload a .json file.
The tool validates instantly — valid JSON is formatted; invalid JSON shows the exact error.
Adjust the indent size (2, 4, 8 spaces, or tab) to match your code style.
Copy the formatted output, or click Minify to compress it to one line.

Why developers use a JSON formatter

Debug AI tool calls: LLMs output JSON in structured responses — validate before parsing in your code.
Read API responses: Format compact API payloads into readable, indented structure.
Catch syntax errors: Locate missing commas, unclosed brackets, and trailing commas fast.
Inspect structure: See total keys, nesting depth, and byte size at a glance.
Minify for production: Compress JSON to reduce payload size for API requests.

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Affiliate disclosure: Some links on this website may be affiliate links. If you click and purchase, we may earn a commission at no additional cost to you. Our recommendations are based on research, usability, pricing, and user needs.

FAQ

Is my JSON data uploaded to a server?

No. This tool runs entirely in your browser using native JavaScript. No JSON is uploaded, stored, or transmitted anywhere.

What does the validator check?

It uses the browser's native JSON parser to check syntax. If the JSON is invalid, it shows the exact parser error message so you can locate the problem — missing commas, unclosed brackets, trailing commas, or unquoted keys.

Can I minify JSON with this tool?

Yes. After validating, click Minify to compress the JSON to a single line with no whitespace, which is useful for API payloads and reducing file size.

Why format AI-generated JSON?

LLMs like Claude, GPT, and Gemini often output JSON in tool calls or structured responses. Formatting and validating that output helps you debug malformed responses, inspect nested structures, and confirm the model returned valid JSON before using it in your code.