No upload - private - browser
Convert JSON and CSV without upload
Updated: May 2026
Some files should not leave your machine: customer exports, internal data, order lists or form results. A no-upload JSON CSV converter transforms the data directly in the browser, without sending it to a remote server for processing.
Free - No upload - Browser-based conversion
Why uploading is a risk
Every time you paste data into an online tool that processes it server-side, a copy travels across the network and lands on a third-party machine. For most data, this is fine. For sensitive data it is not — API tokens, hashed passwords, customer PII, HR exports, financial records, or CRM data containing personal contact information all create legal and operational exposure when uploaded to an external service.
GDPR Article 32 requires appropriate technical measures to protect personal data during processing. Using a server-based tool for personal data creates a processing relationship that may require a Data Processing Agreement with the tool provider. A browser-only tool avoids that relationship entirely.
How local conversion works
When you open the Flowfiles JSON CSV tool, the browser downloads the converter code (HTML, CSS, JavaScript). From that point on, all processing happens in the browser's JavaScript engine — the same engine that runs every website you visit.
When you paste JSON or CSV and click Convert, the transformation executes locally. No network request is sent to Flowfiles or any other server. You can verify this yourself: open the browser DevTools (F12), go to the Network tab, and watch — no requests appear during conversion.
What this means practically
- No server-imposed file size limits — the only limit is your device's RAM.
- Works offline once the page has loaded — you can disconnect from the internet mid-session.
- No data retention — Flowfiles has no database entry for your data because the data never reaches Flowfiles servers.
- No rate limits — you can convert as many times as you want without throttling.
Data types you should never upload to a server-based tool
- API tokens and secret keys — even temporarily stored, these can be leaked in a data breach.
- Hashed or encrypted passwords — hash collisions and brute-force attacks are easier with a copy of the hash.
- Customer personal data — names, emails, phone numbers, addresses covered by GDPR, CCPA or similar regulations.
- CRM exports — often contain a combination of the above in a single file.
- Financial records — transaction histories, account numbers, salary data.
How to do it with Flowfiles
- Load the JSON CSV tool in your browser.
- Optionally disconnect from the internet after the page loads.
- Paste the data to convert.
- Run the conversion and recover the result.
- Clear the editor after you copy or download the output.
Frequently asked questions
Can the page read my files after I close it?
No. The data exists only in the browser's memory during the active session. When you close the tab or navigate away, the JavaScript context is destroyed and the data is gone. Flowfiles has no persistent access to what you pasted.
Is this GDPR compliant?
Using a browser-only tool for processing personal data is significantly lower risk than a server-based tool, because no personal data leaves your device. However, GDPR compliance also depends on how you store, handle and transmit the resulting file — the tool itself is just one step in your workflow.
Is there a file size limit?
There is no server-side size limit because the server is not involved. The practical limit is your browser's available memory — typically several hundred megabytes to a few gigabytes on a modern device. Very large files (over 100 MB of JSON) may slow down the browser UI.
Does it work without an internet connection?
Once the page is loaded, conversion runs entirely offline. Load the tool first, then you can disconnect. If you reload the page without a connection, it will fail to load — but a loaded session can continue without connectivity.
Does data stay in browser memory?
Data stays in memory only while the tab is open and you have not cleared the editor. Closing the tab, refreshing the page, or clearing the input field removes it from memory. Browser history does not record what you pasted — only the URL is stored.
Is it safe on a shared computer?
Be cautious on shared machines. The browser session ends when you close the tab, but if another user opens the browser before the session is cleared, they may see the last active tab. Always clear the editor and close the tab when done on a shared device.