Remove Duplicate Lines
The Remove Duplicate Lines tool finds and removes duplicate lines from your text. It compares each line and keeps only the first occurrence, removing subsequent duplicates. This tool is essential for cleaning up lists, data exports, CSV files, and any text with redundant entries. It can optionally preserve the original order, sort the results, or show only the duplicates. Perfect for deduplicating email lists, product SKUs, or any line-based data.
Formula
Deduplication options: - Case sensitive: 'Apple' and 'apple' are different - Case insensitive: 'Apple' and 'apple' are same - Preserve order: keep first occurrence - Sort result: alphabetize after dedup - Show duplicates: list only the dupes Algorithm: hash set for O(n) lookup
Example
Input: apple banana apple cherry banana Output (preserve order): apple banana cherry Duplicates removed: 2
How to Use
- Paste your text into the input field
- Choose case sensitivity (sensitive or insensitive)
- Select output options (preserve order, sort, or show duplicates)
- Click remove to deduplicate
- Copy the cleaned output
Frequently Asked Questions
How does the tool handle case sensitivity?
By default, the tool is case sensitive: 'Apple' and 'apple' are treated as different lines. You can enable case-insensitive mode to treat them as duplicates. This is useful for cleaning up data with inconsistent capitalization.
Does the tool preserve the original order?
Yes. By default, the tool preserves the order of first occurrences. The first time a line appears, it is kept. Subsequent duplicates are removed. You can optionally sort the result alphabetically.
Can I see which lines were duplicates?
Yes. The tool can show only the duplicate lines (lines that appeared more than once). This helps you identify which entries were repeated in your data.
Does the tool handle empty lines?
Yes. Empty lines are treated like any other line. If you have multiple empty lines, only the first is kept. You can also remove all empty lines separately using the Trim Whitespace tool.
What is the maximum input size?
The tool handles up to 1 million lines in the browser. For larger datasets, use a server-side tool like Python's set() or Unix's 'sort -u' command. The tool is optimized for typical use cases of up to 100,000 lines.