Frequently asked questions

What is JsonPen?

JsonPen is a free online tool to format, validate, and convert JSON, YAML, CSV, and XML. Everything runs in your browser — your data never leaves the device.

Is it really free?

Yes. No signup, no paywall, no rate limit. The tool may eventually show small ads to cover hosting costs, but the core features stay free.

Where does my data go?

Nowhere. Parsing, formatting, and conversion happen entirely in your browser using JavaScript. Nothing is uploaded to a server. The Save button uses your browser's native file picker — the file is created locally and saved to your device.

Does JsonPen support large files?

Files up to 10 MB can be uploaded via the Upload button or drag-and-drop. Larger files may cause the in-browser editor to slow down depending on your device.

Which conversions are supported?

Any direction between JSON, YAML, CSV, and XML. Pick the source format on the Input panel and the target format on the Output panel — the conversion runs immediately.

Why did my conversion to CSV fail?

CSV represents tabular data, so it needs an array of records. A single object converts to a one-row CSV. Top-level primitives (a number, a string) can't be converted to CSV.

Does the tool work offline?

Once the page is loaded, the core editor and conversions work without an internet connection. Analytics calls (when consented) will fail silently when offline.

How do I report a bug or request a feature?

Email info@jsonpen.com.

Which browsers are supported?

Modern Chrome, Edge, Safari, Firefox, and Brave. The native Save As dialog (file system access) works on Chromium-based browsers; Firefox and Safari fall back to a regular download.