Remove Duplicate Lines from Text Online
Remove duplicate lines from text online. Case-sensitive or insensitive. Free, browser-based.
Removing duplicate lines from lists, log files, code, or any text is a common data cleaning task. This tool filters out duplicate lines, keeping only the first occurrence of each unique line. Options include case-sensitive or case-insensitive comparison, and automatic whitespace trimming. After deduplication, the number of removed duplicates is shown so you can verify the result.
How to use
- Paste your text with duplicate lines into the input textarea.
- Choose whether the comparison is case-sensitive and whether to trim whitespace, then click 'Remove Duplicates'.
- The deduplicated text appears in the output with a count of removed lines.
FAQ
What constitutes a 'duplicate' line?
A line is a duplicate if it is identical to a previously seen line, taking into account the case-sensitivity and whitespace-trimming settings. By default, comparison is case-insensitive and leading/trailing whitespace is trimmed before comparison. So ' Hello ' and 'hello' would be treated as duplicates with default settings. Only the first occurrence of each unique line is kept.
Does the tool preserve the original order of lines?
Yes. The first occurrence of each unique line is kept in its original position. Subsequent duplicates are removed. The output order matches the input order — the tool does not sort the lines.
What does 'trim whitespace' do?
When 'Trim whitespace' is enabled (the default), leading and trailing spaces and tabs are removed from each line before comparing. This means ' Hello' and 'Hello ' are treated as the same line. The trimmed version is what appears in the output. Disable this option if you need to preserve whitespace differences between lines.
What is 'case-sensitive' comparison?
When case-sensitive comparison is disabled (the default), 'Hello', 'HELLO', and 'hello' are all treated as the same line. When case-sensitive is enabled, they are treated as three different lines. Enable case-sensitive for deduplicating code, file paths, or other content where case is significant.
Can I deduplicate a list with thousands of lines?
Yes. The deduplication algorithm uses a JavaScript Set for O(n) performance, which is efficient even for very large inputs. A list of 100,000 lines deduplicates in milliseconds in the browser.
Is my text sent to a server?
No. All processing runs entirely in your browser using pure JavaScript. No data is sent to any server, which is important for log files, email lists, or other sensitive text content.