Remove Duplicate Lines: a practical guide

When this is useful

Duplicate-line removal is helpful for lists of URLs, tags, labels, and imported values. Deduplication requires a definition of equality. A case-sensitive identifier list and a human-entered contact list may need different comparison rules.

A reliable workflow

Paste one item per line and choose whether to ignore case or surrounding whitespace. The first matching line is preserved in its original form, and later matches are removed without sorting. The result therefore retains the source’s order.

Example input: apple banana apple

What to check before you finish

Ignoring case can merge distinct case-sensitive paths or IDs. Ignoring surrounding whitespace affects comparison but does not rewrite the first line. Save your original list before replacing it, particularly when a duplicate may represent repeated work rather than redundant data.

Keep the next step simple

Open the Remove Duplicate Lines above to try the workflow. Your input is processed in your browser, without an account or file uploads. The related tools below can help with the next step; check the output before publishing it or adding it to a production system.