JSON Formatter
Format, minify, and validate JSON in your browser. Pretty-print API responses and configuration payloads instantly. No server, no data sent.
JSON Formatter
Runs entirely in your browser — no server calls, no tracking.
Paste JSON and click Format.
🔒 Your data never leaves this tab. This tool has no backend.
About the JSON Formatter
A JSON formatter takes raw JSON — often received as a single-line API response or a minified config — and renders it with consistent indentation so you can read it at a glance. This tool also validates the input: if the JSON is malformed it shows the exact parse error rather than silently producing no output.
When to use pretty vs minify
Use pretty print when debugging API responses, reviewing webhook payloads, or reading configuration files. Two-space indent is the JavaScript convention; four-space matches Python's default json.dumps(indent=4). Use minify when pasting into a <script> tag or a database column where you want compact storage without whitespace overhead.
Common JSON issues
Trailing commas ([1, 2,]) are not valid JSON — they are valid in JS object literals and JSONC but not in JSON spec. Single-quoted strings fail too; JSON requires double quotes. undefined, NaN, and Infinity are not valid JSON values — they will silently serialize to null in JSON.stringify. This formatter catches all of these at parse time.
For large API responses, minifying before storing in logs reduces storage costs significantly. A 10KB pretty-printed response is often 6–7KB minified. At scale — millions of log entries — that difference is measurable.
Format, validate, minify — and convert JSON to CSV
“JSON formatter” covers several jobs that are worth separating, because you usually want a specific one.
| Job | What it does |
|---|---|
| Format / beautify / pretty print | Adds indentation and line breaks so the structure is readable |
| Validate | Reports the exact line and character where the JSON breaks |
| Minify / compact | Strips whitespace for a smaller payload over the wire |
| Convert to CSV | Flattens an array of objects into rows and columns for a spreadsheet |
The first three happen on this page. For the fourth — going from JSON formatter to CSV — use our JSON to CSV converter, which handles the flattening and header generation properly.
The errors that actually cause invalid JSON
Almost every parse failure comes from a short list: a trailing comma after the last item, single quotes instead of double, unquoted keys, a stray comment (JSON has none), or an unescaped quote or backslash inside a string. JavaScript object literals allow several of these, which is why code that runs fine produces JSON that will not parse.
When should JSON be minified?
Minify anything travelling over a network — API responses, config bundles, payloads in a queue. Whitespace can be a meaningful share of a small document. Keep it formatted anywhere a human reads it: files in version control, fixtures, and anything you will debug, where a readable diff is worth far more than the saved bytes.
Nothing leaves your browser
Formatting runs entirely on your device. That matters because JSON pasted into a formatter often contains API keys, tokens, customer records or internal identifiers — none of which should be posted to a third-party server. You can disconnect from the internet and this page still works.
Frequently asked questions
Formatting and converting are different jobs. Format or validate your JSON here first, then use our JSON to CSV converter to flatten it into rows and columns. Conversion works best on an array of objects with consistent keys, since each key becomes a column header.
The usual causes are a trailing comma after the last item, single quotes instead of double quotes, unquoted keys, comments (JSON does not allow any), or an unescaped quote or backslash inside a string. JavaScript object literals permit several of these, which is why valid JS can still be invalid JSON. The validator here reports the exact position.
Formatting (also called beautifying or pretty printing) adds indentation and line breaks so a human can read the structure. Minifying strips every unnecessary character to make the payload as small as possible. Minify for network transfer; keep it formatted for files in version control and anything you need to debug.
It depends entirely on the tool. This one runs completely in your browser — nothing is uploaded, logged or stored, and it works offline. That matters because pasted JSON often contains API keys, tokens or customer data, which should never be sent to a third-party server.
undefined or Infinity. This formatter validates against the strict JSON spec, not JS syntax.jq is faster.Need custom APIs or data pipelines built?
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