Remove Duplicate Lines / Words
Use this free online Remove Duplicate Text tool to strip repeated lines from any list, log file, email export, CSV column or block of text. It is useful for analysts cleaning a list of email addresses before a mail merge, developers de-duplicating log lines, marketers preparing keyword lists, sales teams tidying a CRM export, and anyone who has ever pasted two lists together and noticed the obvious overlap. Paste your text into the box and pick whether the comparison should be case-insensitive and whether whitespace should be trimmed. The tool returns the de-duplicated set ready to copy back into your document. Nothing is uploaded — everything runs in your browser.
How to Use This Remove Duplicate Text
Removing duplicates is a paste-pick-click workflow.
- Paste your list or text into the input area, one item per line.
- Tick the case-insensitive option if 'Apple' and 'apple' should count as the same item.
- Tick the trim-whitespace option to ignore leading and trailing spaces.
- Optionally tick Sort to alphabetise the output.
- Click Remove Duplicates and copy the cleaned list from the output area.
How This Remove Duplicate Text Works
Deduplication compares every line against the lines already kept and discards any line it has seen before. The tool builds a Set in JavaScript, which is the most efficient data structure for this kind of membership check — every lookup runs in roughly constant time, so even a list of 100,000 entries finishes in a fraction of a second. Two optional pre-processing steps change what counts as a duplicate. Case-insensitive matching converts each line to lowercase before comparing, so 'AUSTRALIA' and 'australia' collapse to a single entry. Whitespace trimming strips leading and trailing spaces and tabs, which catches near-duplicates that differ only by indentation. Order is preserved by default — the first occurrence wins — but ticking Sort runs a standard alphabetical sort on the cleaned list. The browser handles everything locally in JavaScript, so even sensitive data such as customer email lists or internal logs never leave your device. For huge lists with millions of rows you would still want a desktop tool or a database, but for the typical few-thousand-row clean-up this tool is faster than firing up a spreadsheet.
Last updated: May 2026.
Frequently Asked Questions
Does it preserve order?
By default yes — it keeps the first occurrence and drops later duplicates. Toggle "Sort Output" to alphabetise the result instead.
Should I use case-sensitive or insensitive?
For email lists or names, case-insensitive is usually right ("ALICE@" and "alice@" are the same person). For passwords or code, case-sensitive prevents losing meaningful distinctions.
Why does the count differ from what I expected?
Empty lines and pure whitespace lines are removed when "Trim Whitespace" is on. Turn it off if you need to preserve them.
Can I dedupe across multiple paragraphs?
Yes — the line mode treats each line independently regardless of paragraph structure. Word mode treats the whole input as a single stream of whitespace-separated tokens.
Is there a size limit?
Practical limit is your browser's memory — millions of lines work fine on modern browsers. Past 10MB or so the page may slow down briefly during processing.