Duplicate Line Remover & Sorter
Remove duplicate lines, sort alphabetically or numerically, trim whitespace, reverse, number lines and clean up any text list instantly. Works great for IPs, domains, keywords, log entries, CSV columns and more.
What is a Duplicate Line Remover?
A duplicate line remover takes a list of text lines — IP addresses, hostnames, log entries, package names, environment variable keys, or any line-delimited data — and produces a cleaned output with repeated lines removed. For DevOps and SRE engineers, this is a practical utility that surfaces constantly when aggregating lists from multiple sources, cleaning up log exports, or preparing input data for scripts and pipelines where duplicate entries cause errors or redundant processing.
Beyond simple deduplication, this tool combines several text processing operations — sorting, whitespace trimming, blank line removal, line numbering, and delimiter conversion — that would normally require piping through multiple Unix utilities (sort -u, awk, tr) or writing a quick Python script. Having all of these capabilities in a browser-based tool means they are available instantly on any machine without needing shell access or scripting knowledge, making the tool equally useful for developers, support engineers, and technical writers.
When to Use This Tool
- IP and hostname deduplication: Merge allowlists or blocklists from multiple sources and eliminate duplicates before loading them into a firewall, WAF, or security group rule.
- Environment variable cleanup: Paste a combined
.envfile assembled from multiple sources and remove duplicate variable definitions that would cause unpredictable behaviour at runtime. - Log analysis preprocessing: Remove repeated log lines from a grep output to see only the unique error messages before investigating root cause.
- CI/CD dependency list normalisation: Deduplicate and sort package lists or image tags collected from multiple Dockerfiles before generating a consolidated dependency report.
How It Works
The tool splits the input text on the selected delimiter (newline by default, with support for comma, tab, and pipe), optionally trims leading and trailing whitespace from each item, then builds a Set data structure — which in JavaScript only stores unique values — to discard duplicates while tracking insertion order for order-preserving deduplication. Sorting operations are applied after deduplication using locale-aware string comparison for alphabetical sorts, character count for length-based sorts, and a native numeric coercion sort for numeric ordering. The result is then joined with the selected output delimiter and displayed with a count of how many duplicates were removed.
Frequently Asked Questions
What operations does this tool support?
The tool supports removing duplicate lines, sorting the result alphabetically (A–Z or Z–A), sorting by line length, sorting numerically, trimming leading and trailing whitespace from each line, removing blank lines, reversing the line order, and numbering each output line. Input and output delimiters are configurable — you can paste a comma-separated list or a tab-separated export and receive newline-delimited output, or vice versa. These operations can be combined: for example, you can trim whitespace, remove duplicates, and then sort alphabetically in a single pass.
Can I process very large lists?
Yes. All processing runs entirely in your browser using JavaScript — no data is uploaded to any server, making it safe for sensitive lists such as internal IP ranges or customer email addresses. The tool handles tens of thousands of lines comfortably on modern devices. For very large inputs (hundreds of thousands of lines), operations like sort-by-length involve an O(n log n) comparison pass and may take a moment to complete; the tool recalculates on every input change so you may notice a brief delay. For extremely large datasets, the equivalent command-line tool is sort -u on Linux, which is optimised for large file processing.
Does duplicate removal preserve the original order of lines?
By default, duplicate removal keeps the first occurrence of each line and discards all subsequent duplicates, preserving the original insertion order of the list. This behaviour is important for use cases like ordered IP allowlists, ranked search results, or configuration files where line order is semantically significant — the cleaned output will have the same sequence as the input, just with repeats removed. If you enable a sort option, the order is replaced by the sort criterion. For cases where you want to find and count duplicates rather than remove them, check the "show duplicate count" option to see how many times each line appeared in the input.