Add Row Numbers to TSV Files Online
Add a row number index column to TSV files directly in your browser. Set the column name and starting number — no upload required.
Drop your .tsv file here
or click to browse — max 50 MB
About this tool
Add a sequential row number column to a TSV file. Set the column name and starting index, then download the updated file. Handy for creating stable IDs or tracking row positions after sorting.
Frequently Asked Questions
Where is the row number column added in the TSV file?
It is added as the first column. You can rename it to anything you like before downloading.
What number does the row index start from?
You can set the starting number — the default is 1. Set it to 0 if your downstream system expects zero-based indices.
Does adding row numbers to a TSV file affect existing data?
No. All existing columns and their values are preserved unchanged. Only the new index column is added.
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.
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