Remove Duplicate Lines strips repeat rows from any pasted list — email addresses, log entries, CSV rows, phone numbers, keywords, or user IDs. By default it is case-sensitive and preserves the original order so the first occurrence wins. An optional case-insensitive mode treats `Foo@example.com` and `foo@example.com` as the same, and an ignore-whitespace mode trims each line before comparing so accidental trailing spaces do not create false duplicates. The tool uses a JavaScript Set for O(n) deduplication, so a 100,000-line list is processed in under a second. It also shows before/after counts, so you can verify how many duplicates were removed. Everything runs in your browser — helpful when the list contains customer emails or other PII you should not upload.
Free, fast, and runs entirely in your browser — no signup, no upload to a server.