Remove Duplicate Lines
Remove duplicate entries from any list or block of text
About this tool
This free duplicate line remover cleans any list of text lines by removing duplicates, with flexible options: keep the first or last occurrence of each duplicate, optionally sort the result alphabetically, trim leading and trailing whitespace before comparing, perform case-insensitive deduplication, and strip blank lines. The result shows how many lines were removed, making it easy to audit the change.
Common use cases: cleaning up email marketing lists where subscribers have been added multiple times, deduplicating a list of keywords before uploading to an SEO or PPC tool, removing repeated entries from a CSV export, cleaning a word list for a dictionary or autocomplete feature, and processing log files where repeated lines add noise. This is a fundamental data cleaning operation in any workflow involving lists.
The case-insensitive option is particularly important for email lists: "John@Example.com" and "john@example.com" are the same address but would not be caught by a case-sensitive deduplicator. Similarly, "Apple" and "apple" should typically be deduplicated together in keyword lists. The whitespace trimming option handles CSV exports where some rows have trailing spaces due to inconsistent data entry.
For very large datasets (millions of rows), a browser-based tool like this may be slow or limited by browser memory. For those cases, command-line tools like Unix sort -u (sort and deduplicate) or awk !seen[$0]++ (preserve order while deduplicating) are faster alternatives. For medium-sized datasets (up to a few hundred thousand lines), this tool handles the task comfortably.