How DataLensia Handles Your Data
A verifiable, step-by-step explanation — not just a promise — of why your JSON and CSV files never leave your browser.
What "100% client-side" actually means
Client-side processing means every operation on your data — parsing, validating, diffing, converting, and rendering — runs inside the JavaScript engine of the browser tab you have open, on your own device's CPU. No copy of your file is ever serialized and sent over the network to a DataLensia server, because DataLensia has no server-side code path that accepts file uploads at all.
Verify it yourself in 60 seconds
Don't take our word for it — this is a claim you can falsify. Here is exactly how:
- Open DevTools. Press
F12(Windows/Linux) orCmd+Option+I(macOS) in Chrome, Firefox, or Edge. - Switch to the Network tab and clear its log (the 🚫 icon).
- Open any DataLensia tool — for example the JSON Validator — and paste or upload a JSON file.
- Inspect every request in the list. You will see only the static assets that were already loading before you added your data (JS bundles, fonts, CSS). No new request fires when you paste, edit, or upload a file.
- Enable Airplane Mode and repeat step 3 — the tool keeps working, which is only possible if it never depended on a network call for your data.
Client-side vs. server-side JSON tools
Most "free JSON formatter" sites process your file server-side, or make this ambiguous. Here's the practical difference:
| Property | Client-side (DataLensia) | Typical server-side tool |
|---|---|---|
| Where parsing happens | Your browser's JS engine | A remote server |
| Data leaves your device? | Never | Yes, on every upload |
| Works offline? | Yes, after first load | No |
| Suitable for regulated data (PII, health, financial)? | Yes — no transmission occurs | Depends on the provider's data handling policy |
| Verifiable by the user | Yes, via browser DevTools (see above) | Not directly — requires trusting the provider |
Frequently asked questions
Does DataLensia upload my JSON or CSV file to a server?
No. DataLensia parses, validates, transforms, and renders every file entirely inside your browser's JavaScript runtime. No fetch(), XMLHttpRequest, or WebSocket call ever transmits your file contents. You can verify this yourself in under a minute — see the steps below.
How can I verify that no network request contains my data?
Open your browser's DevTools (F12 or Cmd+Opt+I), switch to the Network tab, then load a JSON file into any DataLensia tool. Watch the request list: only the initial page assets (HTML, CSS, JS, fonts) are fetched. No request is made after you load or edit your data, and no request body contains your file content.
Can DataLensia work completely offline?
Yes. Once the page has loaded, disconnect from the internet (enable Airplane Mode or disable Wi-Fi) and continue using any tool — the JSON Validator, Comparator, Converter, and Editor all keep working normally, because no part of the processing pipeline depends on a live connection.
Where is my data stored while I use DataLensia?
In your browser's memory (JavaScript heap) for the current session, and optionally in your browser's local storage if you explicitly save a workspace. Nothing is written to any DataLensia-controlled server or database — there isn't one for your file data.
What happens to my data when I close the tab?
It's gone. Unless you explicitly exported it or saved it to a local workspace (stored only in your browser), closing the tab clears the in-memory JavaScript state. DataLensia has no backend record of it because it was never sent anywhere.
Is the 'Share' link feature an exception to the no-upload rule?
No. Share links encode your workspace state directly into the URL itself (using LZ-String/Pako compression), not into a database row on a server. The data travels in the link you copy and paste — DataLensia's servers never see or store it, because the URL fragment is only ever read by the recipient's browser.
Can I backup or collaborate on my workspaces remotely?
Yes, optionally. While DataLensia is local-first and stores your data in your browser, you can link your workspaces to your own personal GitHub repository. This allows you to backup, version-control, and share your transform configurations and notes securely via GitHub sync, without any data passing through our servers.