What the app downloads
The initial page downloads HTML, CSS and a small application shell. CSV, spreadsheet and ZIP engines are self-hosted and loaded only when required. The service worker can cache these application assets for offline use.
What stays local
File names, sheet names, columns, values, samples, filters, recipes and exported files remain in your browser. The app has no business-data upload endpoint.
How to verify it
Open your browser developer tools, select Network, clear the list, then import and process a file. Requests may fetch app assets, but request URLs and payloads must never contain your file content or metadata.
Local storage
Datasets are held in memory by default. IndexedDB stores preferences and recipes only. Temporary browser storage is used for large files when available and is cleared after work. Use Clear local app data to remove preferences, recipes and caches.