FileopiaConvert CSV to JSON
Convert CSV to a JSON array with automatic number/boolean detection and nested objects from dot.keys. Runs in your browser.
- Upload
- Options
- Download
- ✓ 100% free
- ✓ No sign-up
- ✓ No limits
- 🔒 Files never leave your device
How to: CSV to JSON
- Select a CSV file.
- Choose the options.
- Download the JSON.
JSON is the native format for web apps and APIs. Converting CSV to JSON turns spreadsheet rows into objects developers can use immediately.
Common uses
- Seed a database or app with spreadsheet data.
- Prepare data for JavaScript charts.
- Convert exports for an API import.
Tips for best results
- Use headers like address.city to create nested objects.
- Numbers and true/false are detected automatically.
Type detection
Values like 42, 3.14, true and false are converted to numbers and booleans, so the JSON is ready to use in code. Empty cells become null. Text that looks numeric but must stay text, such as postcodes with leading zeros, can be kept by turning type detection off.
Nesting with dot keys
Headers such as address.city and address.zip create a nested address object, which matches the structure most APIs expect.
Why use Fileopia for CSV to JSON?
| Fileopia | Typical upload-based sites | |
|---|---|---|
| Files uploaded to a server | No – processed on your device | Yes |
| Sign-up required | Never | Often for bigger jobs |
| Hourly / daily task limits | None | Common on free plans |
| Watermark on output | Never | Sometimes |
| Works offline after loading | Yes, for most tools | No |
Your files never leave your device
CSV to JSON runs entirely in your browser using JavaScript and WebAssembly. Your files are read from your disk into this tab, processed in memory and saved straight back to your downloads folder – they are never uploaded to Fileopia or any third party.
- Test it yourself: once this page has loaded, switch off Wi‑Fi or mobile data and run the tool – it keeps working.
- Check the network: open your browser’s developer tools (F12 → Network) while processing; you will see no file upload requests.
- Nothing to delete: close the tab and the data is gone – there is no server copy, no retention period and no account.
Frequently asked questions
How are headers used?
The first row becomes the JSON keys. A header like address.city becomes a nested object.
How are headers used?
The first row becomes the JSON keys. A header like address.city becomes a nested object.
Which delimiters are supported?
Comma, semicolon and tab are detected automatically.
Is CSV to JSON really free?
Yes. Every tool on Fileopia is 100% free with no file limits, no sign-up and no watermarks. The site is supported by unobtrusive ads.
Are my files uploaded to a server?
No. Fileopia processes your files directly in your browser using JavaScript. Your documents never leave your device, so they stay completely private.
Does it work on mobile?
Yes. Fileopia works in any modern browser on Android, iPhone, iPad, Windows, Mac and Linux.