Duplicate Line Remover
ContentRemove duplicate lines from any text instantly. Case-insensitive matching, whitespace trimming, keep first or last occurrence. Live side-by-side diff with download.
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About this tool
What is the Duplicate Line Remover?
The Duplicate Line Remover strips repeated lines from any block of text and shows you exactly what changed in a live side-by-side diff. Paste text, upload a file, or type directly — the result updates in real time as you adjust the options.
How to Use It
- Paste or upload your text. Use the paste area, click the Paste button to read from your clipboard, or drag and drop a
.txtor.csvfile onto the input. - Set your options. Configure whitespace trimming, case sensitivity, blank line handling, and whether to keep the first or last occurrence of each duplicate.
- Review the diff. The Before column shows all original lines, with duplicates highlighted in red and struck through. The After column shows the clean output.
- Copy or download. Click Copy to grab the result, or Download to save it as a
.txtfile.
Options Explained
Trim whitespace strips leading and trailing spaces from each line before comparing. With this option on, " apple " and "apple" are treated as duplicates. The original spacing is preserved in the output — only the comparison logic is affected.
Case-insensitive matching ignores capitalization when identifying duplicates. With this on, "Apple", "APPLE", and "apple" are all considered the same line. The version that is kept (first or last) retains its original casing.
Ignore blank lines exempts empty lines from deduplication. All blank lines are passed through to the output unchanged, regardless of how many appear. This is useful when blank lines serve as paragraph breaks or section separators that you want to preserve.
Keep first / Keep last controls which occurrence survives when a duplicate is found. Keep first retains the earliest appearance and removes all later ones. Keep last retains the final appearance. In both cases, the surviving lines appear in their original order in the output.
Common Use Cases
Cleaning word lists and dictionaries — deduplicate vocabulary lists, keyword exports, or dictionary files before importing them into another tool or database.
Processing log files — server and application logs often contain repeated entries for recurring events. Removing duplicates makes it easier to identify unique error types or event patterns.
Deduplicating CSV data — paste a column of values exported from a spreadsheet to quickly identify and remove repeated entries before further processing.
Preparing data for import — many databases and APIs reject imports containing duplicate keys or values. Running the input through this tool first eliminates the problem before it reaches the import step.
Cleaning scraped content — web scrapers often collect repeated lines from navigation elements, footers, or paginated content. Deduplication reduces the noise before analysis.
Privacy
All processing happens entirely in your browser. No text is sent to any server at any point.
How to Use
- 1
Paste or upload your text
Paste text directly into the input area, click Paste to read from your clipboard, or drag and drop a .txt or .csv file onto the input.
- 2
Configure the options
Choose whether to trim whitespace before comparing, enable case-insensitive matching, preserve blank lines, and whether to keep the first or last occurrence of each duplicate.
- 3
Review the diff
The side-by-side diff updates live as you type. The Before column shows all original lines with duplicates highlighted in red and struck through. The After column shows the deduplicated result.
- 4
Copy or download the result
Click Copy in the After column header to copy the output to your clipboard, or click Download to save it as a .txt file.
Frequently Asked Questions
What does "trim whitespace" do?↓
When enabled, leading and trailing spaces are stripped from each line before comparison. This means " apple " and "apple" are treated as duplicates even though they differ in spacing. The original spacing is preserved in the output — only the comparison is affected.
What is the difference between keeping the first and last occurrence?↓
When "Keep first" is selected, the first time a line appears is retained and all subsequent duplicates are removed. When "Keep last" is selected, the last occurrence is retained instead. The output always preserves the original line order.
What does "ignore blank lines" do?↓
When enabled, empty lines are always kept in the output regardless of how many times they appear. This is useful for preserving paragraph spacing or section breaks in formatted text.
Is there a limit to how much text I can process?↓
There is no enforced limit. The tool runs entirely in your browser and processes text as you type. Very large files (tens of thousands of lines) may cause a brief delay as the diff renders.
Can I use this for CSV or code files?↓
Yes. Any plain text file works — .txt, .csv, log files, code files, word lists, or any line-delimited content. Upload the file directly using the Upload button or drag and drop it onto the input area.