Remove Duplicate Lines Online
Eliminate repeated lines from any text instantly. Our duplicate line remover is essential for cleaning data exports, email lists, log files, and any text containing unwanted repetition. Choose to keep the first occurrence or remove all duplicates entirely.
Duplicate Removal Options
| Mode | Behavior | Use Case | Keep FirstPreserves first occurrenceEmail list deduplication Remove AllRemoves every duplicateFinding unique entries only Case Sensitive"Apple" ≠ "apple"Exact matching Case Insensitive"Apple" = "apple"Flexible matching | Trim Whitespace | Ignores leading/trailing spaces | Messy data cleanup |
Duplicate Line Remover Algorithm
``javascript
function removeDuplicateLines(text, options = {}) {
const { caseSensitive = true, keepFirst = true, trimLines = false } = options;
let lines = text.split('\n');
if (trimLines) {
lines = lines.map(line => line.trim());
}
const seen = new Set();
const result = [];
for (const line of lines) {
const key = caseSensitive ? line : line.toLowerCase();
if (!seen.has(key)) {
seen.add(key);
if (keepFirst) result.push(line);
}
}
return {
original: lines.length,
unique: result.length,
duplicatesRemoved: lines.length - result.length,
result: result.join('\n')
};
}
// Example: 100 lines → 75 unique
``
Common Use Cases
Email list cleanup: Remove duplicate email addresses before import to prevent sending multiple messages. CSV data processing: Eliminate repeated rows exported from databases. Log file analysis: Find unique error messages by removing repeated entries. Code cleanup: Remove duplicate import statements or CSS rules.
Performance Considerations
Our tool handles large files efficiently using Set-based deduplication (O(n) time complexity). For files with millions of lines, consider processing in batches. The algorithm preserves original line order while removing duplicates.