List Compare & Duplicate Finder
Find duplicates within a list, or compare two lists to see what matches and what differs — everything runs in your browser, nothing is uploaded.
Common use cases
Email lists
Find subscribers already on your list before importing a new batch.
Product SKUs
Spot duplicate IDs in a catalogue export before uploading to your store.
Keyword research
Merge keyword lists from different tools and remove overlapping terms.
User IDs
Check which users appear in two different cohorts, or find IDs repeated in a report.
Domain names
Compare allowed/blocked domain lists, or deduplicate a crawl output.
Any text list
File names, URLs, tags, order numbers — one item per line is all you need.
Frequently asked questions
Is my data sent to a server?
No. All comparison logic runs in your browser using JavaScript. Your lists are never uploaded, transmitted, or logged — they stay entirely on your device.
What is the difference between "Find Duplicates" and "Compare Two Lists"?
"Find Duplicates" works on a single list and identifies items that appear more than once, showing how many times each one repeats. "Compare Two Lists" takes two separate lists and splits items into three buckets: only in List A, in both lists, and only in List B.
How many items can I compare at once?
There is no enforced limit. The engine uses native JavaScript Set operations and runs entirely in memory, so it handles tens of thousands of lines without slowdown for typical use.
Is the comparison case-sensitive?
By default, the comparison is case-insensitive — "Apple" and "apple" are treated as the same item. Toggle "Case sensitive" in the options bar to treat them as distinct.
Can I compare email addresses, URLs, or IDs?
Yes — the tool works with any text, one item per line. Common use cases include email lists, product SKUs, domain names, user IDs, file names, and keywords.
What does "Trim whitespace" do?
When enabled (the default), leading and trailing spaces are stripped from each line before comparison. This prevents "alice@example.com " and "alice@example.com" from being treated as different items.
Can I export the results?
Yes. Each result panel has a copy-to-clipboard button and a download button that saves the items as a plain .txt file — one item per line.
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