Rowmill

Rowmill is for CSV and TSV files that are too big for Excel, or too sensitive to upload anywhere.

Drop a file and Rowmill shows you every column: its type, blanks, distinct values and distribution. Then build a pivot table the way you would in Excel. Drag fields onto Rows, Columns and Values, click a value to filter, and chart or export the result to CSV or Excel. No SQL and no formulas to learn.

The file stays on your computer. Rowmill reads it inside the browser tab, and once it's open everything keeps working with Wi-Fi off. Rowmill counts every byte it sends and shows the running total, so you can check that none of your file has been sent. Besides anything you type and send yourself, the only thing it sends is a count of which features get used, in coarse buckets, never a file name, a column name or a value. No account, no install.

Measured, not estimated: Rowmill opens 100,000,000 rows at 6 columns (7.8 GB), and a pivot over ten million rows answers in about a second. Excel's grid stops at 1,048,576 rows. Rowmill works the same on a Mac, where Excel has no Power Pivot.

What it can't do:

• It isn't a spreadsheet. You can't edit cells or write formulas.
• It reads CSV and TSV only.
• A single question can use about 3 GB of memory. Sorting a very long or very wide file can take minutes, or not finish.
• Building a pivot needs a window at least 900px wide.

Rowmill is in beta, open to everyone, and free.