Duplicate Remover
Remove duplicate lines from text
1
Total líneas
1
Únicas
0
Duplicadas
0
Eliminadas
Eliminador de Duplicados
Elimina líneas duplicadas de un texto. Puedes elegir eliminar duplicados, mostrar solo los duplicados, mostrar solo las líneas únicas, o contar las ocurrencias de cada línea.
Online Duplicate Line Remover - Clean Up Lists
Duplicate detection modes
This tool offers several modes. Remove duplicates keeps only the first occurrence of each unique line. Show duplicates only lists the entries that appear more than once, which is what you want for an audit. Show unique only lists the entries appearing exactly once. Count occurrences shows each unique line alongside its frequency. Each mode answers a different need: cleaning lists, analysing data, or identifying repeated entries in logs and datasets.
Comparison options
Duplicate detection is configurable. Case-sensitive treats "Apple" and "apple" as different. Case-insensitive treats them as the same and keeps the first one found. Ignore whitespace treats "hello " and "hello" as equal. Unicode normalisation converts composed accented characters to a canonical form. These options matter because invisible duplicates, differing only in spacing or normalisation, are almost impossible to spot by eye yet cause real problems in data.
Use cases for duplicate removal
Removing duplicates is essential for cleaning email lists before a campaign so nobody is contacted twice, preparing data for import into databases with UNIQUE constraints, merging lists from different sources, verifying that a dataset holds no duplicate records, cleaning URL lists before crawling, processing logs by collapsing repeated events, and building unique sets of tags or categories. Everything is processed locally, which makes it safe for sensitive data.
If you work with this tool, you will probably also find these useful Text Diff Checker, Word Counter, String Utilities, Text Diff.
Frequently asked questions
Why are entries that look identical not detected as duplicates?
The usual invisible differences are trailing spaces at the end of a line, a non-breaking space (code 160) instead of a normal space (code 32), different line endings (CRLF versus LF), and homograph Unicode characters such as a Latin "a" against a Cyrillic one. Turn on the normalisation and trim options to catch them.
Can I keep the original order while removing duplicates?
Yes, this tool preserves first-appearance order. If "banana" shows up on lines 1, 5 and 9, line 1 survives and the others are dropped, so the result keeps the original sequence of unique entries.
Is there a limit on how many lines I can process?
Processing happens in your browser, and lists of several thousand lines complete instantly. With millions of lines you may notice slowdowns, in which case a command line tool such as sort -u or awk is a better fit for the file size.
How do I remove duplicates based on only part of each line?
This tool compares whole lines. To deduplicate by a specific field, such as the email column of a CSV, preprocess the data: extract the relevant column, find the duplicates and then filter the original lines. Tools such as awk or a short Python script handle that far better.