Spreadsheet for Big Data: Open Giant CSV and Parquet
Open spreadsheets that Excel and Google Sheets cannot. Drop a multi-gigabyte CSV or Parquet file with millions of rows and scroll, sort and explore it instantly, all in your browser. There is no upload and no size cap from a server, because the data is read and queried locally with DuckDB-WASM, a fast columnar engine. Your file never leaves your device, which makes this safe for sensitive data that you cannot put in a cloud spreadsheet.
How to open a big spreadsheet
- Drop a CSV, TSV, Parquet, JSON/JSONL or .gz file (multi-GB and millions of rows are fine).
- Scroll the grid; rows stream in on demand so it stays fast even at tens of millions of rows.
- Click a column header to sort ascending, descending, or off.
Examples
Opening a 31 million row CSV
events.csv (4 GB, 31,000,000 rows)
An interactive grid you can scroll and sort instantly, with nothing uploaded.
Frequently asked questions
How big a file can it open?
Tens of millions of rows and multi-gigabyte files, far beyond Excel's ~1,048,576 row limit and what Google Sheets allows. The file is streamed and queried with DuckDB-WASM in your browser rather than loaded all at once, so it stays responsive. Truly enormous files are bounded by your device's memory, not a fixed cap.
Is my data uploaded anywhere?
No. The file is opened and queried entirely in your browser with DuckDB-WASM. Your data never leaves your device, so this is safe for confidential data you could not put into a cloud spreadsheet.
What file formats are supported?
CSV, TSV, plain text tables, Parquet, JSON and JSONL/NDJSON, including gzip-compressed (.gz) versions. Parquet is recommended for the largest datasets because it is columnar and compresses well.
Why is it so fast on big files?
It uses DuckDB-WASM, a columnar analytical database compiled to WebAssembly, and a virtualized canvas grid that only renders the rows on screen. Sorting and scanning run as database queries over the columns, so a sort or aggregate over millions of rows completes in a fraction of a second.
Does the first load take a moment?
The first time you open a file, the browser downloads the DuckDB-WASM engine (a few megabytes) and caches it. After that it loads instantly and works offline.
Can I export or download the data?
Yes. Use Export to download the current tab, including any pivot, filter or SQL result, as a CSV or Excel (.xlsx) file. The export honors your active filters, so you get exactly the rows you see. Everything is generated in your browser, so nothing is uploaded.
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