Duplicate Line Remover
Deduplicate lists and log lines while preserving first-occurrence order, with optional case-insensitivity and whitespace trimming.
About the Duplicate Line Remover
The Duplicate Line Remover scans each line in order and retains only the first occurrence of every unique line. Enabling Case-insensitive treats POST /orders and post /orders as duplicates, and enabling Trim surrounding whitespace strips leading and trailing spaces before comparing.
Order-Preserving Hash Set
Uses an in-memory JavaScript Set to deduplicate thousands of lines in O(n) linear time while preserving the exact first-seen order of your original list.
Whitespace & Case Normalization
Eliminate hidden duplicates caused by trailing spaces, Windows CRLF line endings, or inconsistent capitalization across CSV columns, email lists, or log files.
Live Deduplication Metrics
View exact counts of Original Lines, Unique Lines Kept, and Duplicates Removed immediately after each run.
Frequently Asked Questions
Does removing duplicates change the order of the remaining lines?
No. Unlike command-line sort -u which forces alphabetical sorting, this tool preserves the original chronological or positional order of the first occurrence of each line.
What happens to empty lines in my input?
If Remove blank lines is checked, all empty or whitespace-only lines are stripped completely. Otherwise, at most one blank line is kept at its first occurrence.