Use DuckIt. Drop a CSV or TSV and it converts to Parquet entirely in your browser using DuckDB-WASM (no server upload) - you can download the Parquet locally for quick analysis. To get an actual DuckDB database with a shareable link, the browser uploads the Parquet and a FastAPI backend converts it to DuckDB and returns a time-limited, signed shareable URL (usable from xlwings Lite or any app).
So the split is deliberate: CSV to Parquet in-browser; Parquet to DuckDB on the backend. Stack: React + DuckDB-WASM frontend, FastAPI backend, signed URLs with three storage tiers.
Live app: https://www.tigzig.com/duckit-xlwings. Open-source repo: https://github.com/amararun/DUCKIT_UPLOADER-final. To query a DuckDB/CSV entirely in-browser with AI, see BRIQ at https://www.tigzig.com/briq.
Building something like this? How I work covers the rates, the availability and what I take on.