Remove Duplicate Lines

What Is the Remove Duplicate Lines Tool?

The Remove Duplicate Lines tool scans through your text and deletes any line that has already appeared earlier in the block, keeping only the first occurrence of each unique line. It processes the whole thing in one click. It is useful for cleaning up lists that have been merged from multiple sources, deduplicating exported data, or tidying up any text where repeated lines have crept in and need to go.

The output keeps the original order of the lines intact, just with the repeats removed. Which is usually exactly what you want, though it is worth knowing that is how it works before you run it on something order-sensitive.

How to Use This Tool

1. Paste or type your text into the input box above. Each line in the input is treated as a separate item.
2. No settings needed. The tool compares lines as-is and removes any that are exact duplicates of an earlier line.
3. Click Remove Duplicate Lines and the tool returns your text with all repeated lines stripped out, leaving only unique lines in their original order.
4. Copy the result using the Copy button, or select and copy manually. Use Clear to reset the input.

When Would You Use This?

Cleaning up a list of email addresses, names, URLs, or keywords that was assembled from multiple places and ended up with the same entries appearing more than once.

Deduplicating exported or copied data before importing it into a spreadsheet, database, or tool that expects each entry to be unique and would behave oddly with duplicates in the input.

Tidying up a merged text file or combined output from multiple sources where the same lines got included several times and the whole thing needs to be collapsed down to just the distinct entries.

Examples

Removing duplicate entries from a simple list

Input   : apple
banana
apple
kiwi
banana
mango
Output  : apple
banana
kiwi
mango

Deduplicating a list of email addresses

Input   : alice@email.com
bob@email.com
alice@email.com
carol@email.com
bob@email.com
Output  : alice@email.com
bob@email.com
carol@email.com

Cleaning up a merged keyword list

Input   : text tool
word count
text tool
character counter
word count
line counter
Output  : text tool
word count
character counter
line counter

Multiple blank lines collapsed

Input   : line one
/
line two
/ line three
Output  : line one
/ line two
line three
(Consecutive blank lines reduced to one blank line since all blanks are treated as identical)

Frequently Asked Questions

How do I remove duplicate lines from a text file?

Paste the contents of your text file into the input box and click Remove Duplicate Lines. Copy the output and save it back to your file. Each line that appeared more than once will be reduced to a single occurrence.

Does it keep the first or last occurrence of a duplicate line?

It keeps the first occurrence and removes any subsequent copies. So the order of the remaining lines matches the original order, just with the repeated entries taken out.

Is the comparison case sensitive?

Typically yes, meaning "Apple" and "apple" would be treated as two different lines and both kept. If your duplicates differ only in casing, you may want to standardize the case first before running the deduplication.

How do I remove duplicates in Excel?

Select your data and go to Data, then Remove Duplicates. You can choose which columns to check for duplicates. For plain-text lists outside of Excel, pasting into this tool is faster.

How do I remove duplicate lines in Notepad++ ?

Go to TextFX, then TextFX Tools, and select Sort lines case sensitive or Sort lines and remove duplicates. Note that this sorts the lines alphabetically as part of the process. If you need to preserve the original order while removing duplicates, this tool does that without reordering.

How do I deduplicate a list in Python?

The simplest way is to use a dict or ordered set to preserve order while removing duplicates: list(dict.fromkeys(lines)). For a quick one-off cleanup without code, paste the list into this tool instead.

What counts as a duplicate line?

An exact match of the full line content, including any leading or trailing spaces. Two lines that look the same but have different spacing may not be treated as duplicates depending on how they were entered.

Does it remove blank lines too?

Blank lines are treated as lines like any other. If you have multiple blank lines in a row, they would be collapsed to one. If that is not what you want, it is worth checking the output.

Can I use this on a list with thousands of lines?

No hard limit is set. For large lists the tool processes the whole block, though very large inputs may take a moment.