Duplicate Line Remover
Remove duplicate lines from text with case-insensitive matching and keep-first/last options.
Input Text (one item per line)
Keep occurrence
Options
About This Tool
The Duplicate Line Remover scans each line and removes any that has already appeared, producing a set of unique lines. You can choose to keep the first or last occurrence of each duplicate.
Case-insensitive mode treats "Apple" and "apple" as identical. Whitespace trimming normalizes lines before comparison. All processing happens locally in the browser.
How to Use
- Paste lines of text or click Sample to load an example.
- Choose whether to keep the First or Last occurrence of duplicates.
- Toggle Case-sensitive, Trim whitespace, and Remove empty lines as needed.
- Click Remove Duplicates and copy the result.
Use Cases
Developers deduplicate lists of IDs, emails, or domains exported from a database. Data analysts clean survey responses or repeated CSV column values. Writers remove repeated terms from word lists or glossaries.
FAQ
- Is order preserved? — Yes. In "keep first" mode the output preserves original order keeping the first occurrence. In "keep last" mode it keeps the last occurrence.
- What counts as a duplicate? — By default (case-insensitive, trim enabled), two lines are duplicates if their trimmed, lowercased content is identical. Enable case-sensitive mode for exact matching.
- Is there a size limit? — No. Large inputs with thousands of lines are handled efficiently using a hash set (O(n) time).