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Lines are compared after optional normalization (trim whitespace, case-insensitive). A hash map tracks first occurrences; subsequent matches are flagged as duplicates with their line numbers.
Algorithm: O(n) hash-based scan; Memory: O(unique lines); Comparison: exact or normalizedResults can show: only duplicate lines, only unique lines, duplicate lines with occurrence counts, or all lines with duplicate markers. Group-by mode clusters identical lines together.
Updated: July 2026
Identify repeated rows in a data export to clean before database import.
→ List of duplicate lines with line numbers and occurrence count
Remove duplicate URLs from a crawl list, keeping first occurrence of each.
→ Unique URL list with duplicate count summary
Trailing spaces, tabs, or different line endings (\r\n vs \n) cause identical-looking lines to be missed. Always trim whitespace and normalize line endings before comparison.
In structured data (CSV, TSV), duplicates may only apply to a specific column. Use the column extractor first to isolate the key field before checking for duplicates.
Find duplicate lines in text instantly. Highlight repeated rows in logs, CSV data, and code lists. Free online text analysis tool with no upload required. It applies the duplicate detection (Algorithm: O(n) hash-based scan; Memory: O(unique lines); Comparison: exact or normalized). For example: find duplicate entries in a csv — Identify repeated rows in a data export to clean before database import.