How to Remove Duplicate Lines From Text

Duplicate entries creep into every list. A mailing list with the same address twice, a merged file with repeated rows, a log with identical lines, a keyword list with accidental copies. Removing duplicate lines strips the repeats and leaves each unique line once. This guide explains how de-duplication works, the settings that change the result, and how to combine it with sorting.

What de-duplication does

The tool scans your list line by line and removes any line that has already appeared, keeping only the first occurrence of each unique line. A list of 500 entries with 80 repeats becomes a clean list of 420 uniques. It is one of those quiet tasks that is tedious by hand and instant with a tool.

How to remove duplicate lines with this tool

1. Open the Remove Duplicate Lines tool.
2. Paste your list, one item per line.
3. Remove duplicates.
4. Copy the de-duplicated result.

Everything runs in your browser, so your list — often contacts or data — is never uploaded.

The settings that decide what counts as a duplicate

"Duplicate" is less obvious than it sounds, and these options change the outcome:

• Case sensitivity. Is `Apple` the same as `apple`? Case-sensitive treats them as different; case-insensitive treats them as the same. For most real lists — emails, names — case-insensitive is what you want, because `Bob@x.com` and `bob@x.com` are the same person.
• Whitespace. A line with a trailing space is technically different from one without. Trimming whitespace before de-duplicating catches "invisible" duplicates that otherwise slip through — clean with Remove Extra Spaces first.
• Blank lines. Decide whether empty lines should collapse to one or be removed entirely.

De-duplicate, then sort (or the reverse)

De-duplication and sorting are natural partners. A common workflow:

1. Trim whitespace so near-identical lines match.
2. Normalize case with Convert Case if case variants should count as the same.
3. Remove duplicates here.
4. Sort the clean list with Sort Lines for a tidy, ordered, unique result.

Common uses

• Clean a mailing list of repeated addresses.
• De-duplicate merged data from several sources.
• Collapse repeated log lines.
• Tidy a keyword or tag list.

Related tools

Pair with Sort Lines, Remove Extra Spaces, and Convert Case for a full list-cleanup pass. Comparing two lists for differences instead? Diff Checker.

Common uses

• Unique lists from messy data.
• Deduplicate contacts or entries.
• Clean before importing.

Privacy and limits

De-duplication is fully local — no upload, nothing stored, offline once loaded. Open the Remove Duplicate Lines tool to keep each line once.