JSON Tools
A single place to format, minify and validate JSON, plus convert between JSON and CSV. Everything runs in your browser — no upload.
Input
Output
A complete JSON workbench in your browser
JSON is everywhere — API responses, config files, NoSQL exports, log entries. This page bundles the operations developers and analysts need every day:
Format (pretty-print)
Turn a one-line minified blob or messy hand-written JSON into a clean, indented document. Choose 2 spaces, 4 spaces or a real tab character. Useful for reading API responses, sharing snippets in bug reports, or pasting into documentation.
Minify
Strip every unnecessary character from JSON to ship the smallest possible payload. Typical savings are 20-40% on real-world data; on heavily indented configs the savings can hit 60%. The status bar shows the exact byte difference and percent saved.
Validate
Verify your JSON parses cleanly. On error, we display the engine's message plus a guessed line and column number with a 2-line snippet showing exactly where parsing broke. This works even in browsers and runtimes that no longer include positions in error messages — we figure it out ourselves.
JSON ↔ CSV
Convert an array of objects to CSV with one click. Nested objects are flattened with
dot-notation (so {"user":{"name":"Alice"}} becomes a column user.name).
Nested arrays are serialized as JSON strings inside their cells. Rows with different keys produce
the union of all columns — missing fields become empty cells. The CSV → JSON direction handles
quoted fields, embedded commas, and escaped quotes correctly (we use the battle-tested
PapaParse library).
Privacy
Everything runs locally. Your JSON, your CSV, your secrets — none of it leaves the browser tab. The only network request is the one-time CDN load of PapaParse. We don't even see file sizes.
Common use cases
- Pretty-print an unreadable API response from
curl. - Minify a config file before embedding it in a script.
- Validate a JSON Schema document or LLM-generated structured output.
- Export a spreadsheet to JSON for use in a frontend app.
- Convert API results to CSV for analysis in Excel or Google Sheets.
Frequently Asked Questions
- How do I format JSON online?
- Paste your JSON into the input field and click Format. The tool instantly pretty-prints it with your chosen indentation (2 spaces, 4 spaces, or tabs). Everything runs entirely in your browser — no data is uploaded to any server.
- Does this JSON tool upload my data to a server?
- No. All formatting, minification, validation, and conversion happen entirely in your browser tab using JavaScript. Your JSON never leaves your device. The only network request is the one-time CDN load of the PapaParse library for CSV conversion.
- Can I convert JSON to CSV and CSV to JSON?
- Yes. Click JSON to CSV to convert an array of objects into a downloadable CSV file. Nested objects are flattened with dot-notation. For the reverse, paste CSV data and click CSV to JSON — it handles quoted fields, embedded commas, and escaped quotes correctly using the PapaParse library.
- What happens when my JSON has a syntax error?
- The Validate function detects syntax errors and shows you the exact line and column number where parsing failed, along with a 2-line code snippet. This works even in environments that no longer include position info in error messages — our tool calculates it independently.
- Is this JSON formatter really free?
- Yes, completely free with no limits. There is no signup, no account, no file-size cap, and no premium tier. You can format, minify, validate, and convert as many times as you want. The tool is supported by optional ads only.