How to remove duplicate lines without breaking your data

Copying a customer list out of a CRM or a spreadsheet and then hunting duplicates by eye. The duplicates are never adjacent: a name appears at row 3 and again at row 900 with different capitalisation.

You see this most often in email lists before an export, SKU lists before a supplier upload, log files after a retry storm. Excel Remove Duplicates is case-insensitive by default and silently keeps the first match, so you cannot see what it dropped.

Doing it in four steps

1. Paste the lines into the box
2. Decide whether case and spaces should count
3. Read the removed count before you copy anything
4. Copy the clean list

The whole thing runs locally in the browser tab: no upload, no account, no queue. When the page says "removed 37 lines", that number comes from the file you just pasted, not from a sample.

The report tells you how many lines were removed before you copy anything, so a collapsed list is never a surprise after the fact.

For the full picture — imports, feeds, variants, identifiers — see the pillar guide: Shopify product data management.

Try it on your own file

Open Remove Duplicate Lines and paste a sample. It is free, it does not store anything, and you do not need an account. If the file is sensitive, save the page locally and run it offline.

Questions people ask

Does it handle trailing spaces?

Yes — trimming is on by default, so " apple" and "apple" collapse into one line.

Is my list uploaded?

No. The page runs entirely in your browser; you can save it and use it offline.