About Remove Duplicate Lines
Duplicate lines appear frequently in data exports, log files, keyword lists, and text gathered from multiple sources. Manually finding and removing them is tedious and error-prone, especially with large datasets. This tool automates the deduplication process: paste your text (one item per line), choose whether to keep the first or last occurrence of each duplicate, and get a clean list instantly. You can also remove empty lines in the same pass. It is a simple yet powerful utility for anyone who works with text data regularly.
How to Use Remove Duplicate Lines
- Paste your text into the input area (one item per line).
- Choose whether to keep the first or last occurrence of each duplicate.
- Optionally check Remove empty lines to strip blank entries.
- Click Remove duplicates. The deduplicated result appears in the output.
- Copy the clean list for use in your project, spreadsheet, or file.
Key Features
- Removes exact duplicate lines while preserving the chosen occurrence
- Option to keep first or last occurrence of each duplicate
- Optional empty line removal for cleaner output
- Handles large text inputs efficiently
- Entirely browser-based — no data uploaded to any server
When to Use This Tool
- Cleaning keyword or tag lists that contain repeated entries
- Deduplicating email lists, URLs, or data exports before processing
- Tidying up log files or console output that repeats messages
- Consolidating text merged from multiple sources
- Preparing unique-value lists for import into databases or spreadsheets
Technical Details
The tool splits the input on newline characters, iterates through the lines, and uses a Set to track lines already seen. If "keep first" is selected, the first occurrence is retained and subsequent duplicates are discarded. If "keep last" is chosen, the array is processed in reverse. Comparison is exact (case-sensitive and whitespace-sensitive). For case-insensitive deduplication, normalize the text first using the Case Converter. For line sorting before or after deduplication, try the Sort Lines tool.
Conclusion
Removing duplicate lines is a common data-cleaning task that this free, browser-based tool handles instantly. Paste your text, choose your settings, and get a clean, unique list — privately and with no sign-up required.