JSON to CSV Converter – Flatten Nested JSON Online
Paste JSON and get a spreadsheet-ready CSV with nested fields flattened, or turn CSV back into JSON. Everything runs in your browser; nothing is uploaded.
- 100% free
- No sign-up
- Nothing uploaded
- No watermark
- No limits
- No bullshit
JSON input
CSV output
How to use
- Paste or drop JSON. An array of objects works best, but a single object, or an object that contains an array (like an API response with
{"data":[…]}), is handled automatically. - Check the flattening. Nested objects become
address.citycolumns and arrays becometags[0],tags[1]. Lower the depth to keep deeper structures as JSON strings. - Copy or download the CSV. Tick "UTF-8 BOM" if you will open it in Excel and the file has accents or emoji.
FAQ
How are nested objects converted to CSV?
Each nested key becomes its own column using dot notation, so {"a":{"b":1}} produces a column called a.b. Arrays use bracket indexes: items[0].name. The header is the union of every key found in any row, in the order they first appear, so rows with missing fields simply get empty cells.
What if my JSON is not an array?
A single object becomes a one-row CSV. An object that wraps an array (for example {"results":[…]}) is unwrapped automatically — the first array found is used. Arrays of plain values are exported as a single value column.
Why does the tool say my JSON is invalid?
Common causes are trailing commas, single quotes instead of double quotes, unquoted keys, or comments. The error message includes the line and column where parsing stopped so you can fix it quickly.
Can I convert CSV back to JSON?
Yes. Switch to CSV → JSON: the first row becomes the keys, values that look like numbers, booleans or null are converted (toggle this off to keep everything as strings), and flattened headers like address.city are rebuilt into nested objects.
Simple Desk Tools vs. the usual suspects
| This tool | Typical "free" tool sites | |
|---|---|---|
| Price | Free, forever | Free tier, then paywall |
| Account | None — open the page and go | Sign-up or email required |
| Your files | Stay on your device; nothing is uploaded | Uploaded to their servers, kept for hours |
| Watermark | None | On the free tier |
| Limits | None — any size, any number of files | Daily caps and file-size limits |
| Speed | Instant — runs in your browser | Queue, upload, wait, download |
The no-bullshit promise: no registration, no upsell, no "premium" button, no watermark, no file limits, and your files never leave your computer. The site is paid for by a couple of ads, nothing else.
Privacy: your data never leaves the browser. There is no server and no upload.