Does it work offline?

Yes — once the page is loaded, everything runs locally with no network calls.

What's the maximum size?

Your browser's memory is the only limit. Files up to a few megabytes feel instant; multi-megabyte payloads may take a moment to parse.

Does it accept JSON5 or JSONC (with comments)?

No, only strict JSON per RFC 8259. Strip comments and trailing commas before pasting.

Is my data sent anywhere?

No. All parsing, formatting, and diffing happens in your browser. Nothing is uploaded — the AI summary uses Chrome's on-device Gemini Nano, so even AI runs locally.

How does the AI Explain button work?

It uses Chrome's built-in Prompt API (Gemini Nano), which runs the model on your device. There's no API call to OpenAI / Google / anyone — your JSON never leaves your machine. The button only shows up if your browser supports it (Chrome 138+, with the optional model downloaded). On every other browser the tool works normally without it.

JSON Formatter

Format, validate, minify, diff, and explore JSON — all client-side.

Empty input

Input

Formatted output

Enter valid JSON to see formatted output.

How to use it

1Paste your JSON into the input editor.
2Switch modes: Format (pretty-print), Minify (single line), Tree (collapsible explorer), or Diff (compare two payloads).
3Copy the result, or click through the tree to drill into nested keys.
4On Chrome with the Prompt API enabled, hit Explain to get a 2–4 sentence Gemini Nano summary of what the payload is and what its key fields mean.

Common use cases

Debug API responses and find malformed or missing fields.
Minify a payload to fit inside a query parameter or test fixture.
Diff a before-and-after payload to track exactly what changed.
Drill into deeply nested configuration files with a collapsible tree.
Get a plain-English summary of an unfamiliar webhook or API payload via on-device AI.

Frequently asked questions

Does it work offline?: Yes — once the page is loaded, everything runs locally with no network calls.
What's the maximum size?: Your browser's memory is the only limit. Files up to a few megabytes feel instant; multi-megabyte payloads may take a moment to parse.
Does it accept JSON5 or JSONC (with comments)?: No, only strict JSON per RFC 8259. Strip comments and trailing commas before pasting.
Is my data sent anywhere?: No. All parsing, formatting, and diffing happens in your browser. Nothing is uploaded — the AI summary uses Chrome's on-device Gemini Nano, so even AI runs locally.
How does the AI Explain button work?: It uses Chrome's built-in Prompt API (Gemini Nano), which runs the model on your device. There's no API call to OpenAI / Google / anyone — your JSON never leaves your machine. The button only shows up if your browser supports it (Chrome 138+, with the optional model downloaded). On every other browser the tool works normally without it.