Useful Commons

Free browser tool

Merge CSV files

Choose CSV files that share the same header. They are stacked in order into one CSV, each row labelled with the file it came from, and every input row is accounted for. Nothing is joined, deduplicated or converted.

Runs on this device. No upload, account or tracking; nothing is scheduled or applied.

Your CSV files

Files are read on this device. Each file's name, without its extension, becomes its source label.
Advanced: paste files as JSON

[{"label": "north-2026-09", "csv": "sku,qty\n00123,4\n"}, …]; an optional per-file "delimiter".

Options

Export for

Spreadsheet puts an apostrophe before text that starts with =, +, - or @, so a spreadsheet never runs it as a formula. Machine import keeps the exact text.

2 to 20 files, 250,000 bytes (UTF-8) each and 500,000 bytes in total, up to 5,000 rows. Headers must match exactly and in the same order.

About this tool

What this tool does

Combine 2 to 20 CSV files with the same columns into one CSV, with a source column on every row and a full row count check, without uploading them.

Limits and safe use

2 to 20 files, 250,000 bytes (UTF-8) each and 500,000 bytes in total, up to 5,000 rows. Headers must match exactly and in the same order. Review the report before relying on it. It is a deterministic check, not a certification, and it does not send data to a server or a model.