Duplicate Line Remover
Remove duplicate lines from any text, with optional case sensitivity.
How to use this tool
- 1Paste your lines into the left Input panel — the line count is shown in the label.
- 2Toggle 'Case-sensitive comparison' to control whether 'Hello' and 'hello' are treated as duplicates.
- 3The right Output panel shows the unique lines and how many were removed.
- 4Click Copy to copy the deduplicated output.
About Duplicate Line Remover
Cleaning up lists with repeated entries — email addresses, keywords, product SKUs, log lines — is a common data preparation task. This tool splits your input on newlines, tracks seen lines in a Set for O(n) performance, and outputs only the first occurrence of each line. A case-sensitive toggle controls whether 'Apple' and 'apple' are treated as the same line: when checked, comparison is exact; when unchecked, both are lowercased before comparison but the original casing of the first occurrence is preserved in the output. The output panel shows the line count and how many duplicates were removed, so you can verify the result before copying. Paste a list of 10,000 email addresses and get the unique set in milliseconds. Runs entirely in your browser — no file upload, no server.