Sample CSV Files Online

What sampling methods are available for CSV files?

First N rows, last N rows, or a random sample of N rows. First and last are deterministic. Random sampling uses a reservoir algorithm for an unbiased selection.

Is random sampling of a CSV file reproducible?

No — each run produces a different random sample. For a reproducible result, use the SQL Query tool and write SELECT * FROM table USING SAMPLE reservoir(N ROWS) REPEATABLE(seed) with a fixed seed number.

Does sampling a large CSV file read the whole file?

First N and last N rows are very fast — the tool stops reading early. Random sampling scans the full file to ensure an unbiased selection.

Is my data private?

Yes — completely. Your file is never uploaded to any server. Everything runs locally in your browser using WebAssembly — processing happens entirely inside your tab. Once you close the tab, nothing is retained.

What is the maximum file size?

The free limit is 50 MB. For larger files, performance depends on your device's available memory — most modern machines handle 500 MB to 1 GB comfortably.