Convert JSON to CSV without uploading the file. API responses, database dumps and export files arrive as JSON; finance, operations and almost everyone who has to actually read the data want a spreadsheet. When that JSON holds customer records, transactions or anything covered by a data-protection obligation, pasting it into a random online converter is the part of the workflow nobody documents. In Sensitive mode this runs inside your browser tab, so the records never leave the machine.
How to use JSON to CSV
- Choose your privacy mode. Sensitive keeps the data on this device; Ordinary uploads it to our server for very large files.
- Select a .json file containing an array of objects — the shape an API or a database export normally produces.
- Pick the delimiter for the output: comma, semicolon or tab. Semicolon suits European Excel, which treats commas as decimal separators.
- Click Process and download the .csv, ready to open in Excel, Numbers, Sheets or anything else that reads a spreadsheet.
Worked example
A nested API export flattened into columns finance can actually open
An orders endpoint returns 2,000 records where each order carries a nested customer object and an array of line items: customer.name, customer.address.city, and items holding three or four entries. CSV has no nesting, so something has to give. Nested keys are flattened with dot notation — customer.address.city becomes a column of exactly that name — and array values are JSON-encoded inside their cell rather than being silently dropped or spread across unpredictable extra columns. Column order follows first appearance across the whole file, not just the first record, so an optional field that only shows up on record 700 still gets a column instead of being lost. The records include names and addresses, so run it in Sensitive mode.
Processing limits & specifications
| Mode | Location | Max file size | Retention |
|---|---|---|---|
| Sensitive mode | Your device (WASM) | Up to 30 MB (typical device) | Never stored / zero egress |
| Normal mode | Server sandbox | 200 MB | Deleted when you close the page |
Frequently asked questions
Can I convert JSON to CSV without uploading the file?
Yes. In Sensitive mode the conversion happens inside your browser tab. Open the Network tab, run a file through, and nothing carrying your data appears — that page is not permitted to make outbound requests at all.
Is it free? Any signup or size limit?
Free, no account, no email, no watermark. The only limit is your device's memory, shown on the page before you pick a file.
What happens to nested objects?
They are flattened with dot notation, so customer.address.city becomes a single column with that exact name. Nothing is discarded to make the data fit.
What happens to arrays inside a record?
The array is JSON-encoded into its cell. That keeps the value intact and reversible, rather than dropping it or scattering it across a variable number of columns that would break the header.
What if records have different fields?
Column order follows first appearance across every record, not just the first one, so a field that only appears late in the file still gets a column.
My JSON is a single object, not an array. Will it work?
A single object is treated as a one-row export. For anything else the file needs to be an array of objects — that is the only shape with a sensible mapping onto rows and columns.
What happens if the JSON is invalid?
You get a clear error rather than a corrupt half-written CSV, so you can fix the source instead of discovering the problem in a spreadsheet later.
Can I use semicolons for European Excel?
Yes. Choose semicolon or tab as the delimiter — semicolon is what Excel expects in locales where the comma is a decimal separator.
Does it work offline?
Yes, once the page has loaded. Sensitive mode makes no network requests.
Do you keep a copy of my data?
In Sensitive mode we never receive it. In Ordinary mode the file is encrypted at rest and deleted when you close the window, five minutes after you download, or fifteen minutes after processing finishes.