Local-first data processing

Your browser reads the selected file and sends work to a dedicated Web Worker where supported. The worker returns a generated Blob for download; the source file is not sent to a HappyCSV server.

Excel parsing and other heavier operations run inside the worker to keep the interface responsive. Browser memory still matters, so tools enforce a 100MB per-file limit and show progress or errors when available.

Analytics measure aggregate site usage. They are separate from the file-processing path and do not receive uploaded file contents.