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Merge Lists & Find Duplicates
The Merge Lists & Find Duplicates tool combines several lists of text into one and shows you exactly how they overlap: the de-duplicated union, every item merged with duplicates kept, the items that appear in two or more lists, and the items unique to each list. It is built for the everyday list-wrangling that fills an SEO workflow, comparing keyword exports, reconciling backlink sets, or finding which domains two prospecting lists have in common.
It is completely free and runs entirely in your browser. Paste your lists, toggle trimming, case-sensitivity, and blank-line handling, and the counts and result panels recompute instantly with real JavaScript Set logic. Nothing you paste is sent to a server.
🔒 Private: everything runs in your browser. Nothing you paste is uploaded.
How to merge lists and find duplicates
Paste one item per line into each list, pick how items should be compared, then switch between the four result panels. Each panel shows a live count and a Copy button.
Choose how items are compared before you read the counts
The three options decide what counts as a match. Trim whitespace removes leading and trailing spaces so a stray tab no longer makes two identical entries look different. Case-insensitive treats Example.com and example.com as the same item, which matters when comparing exports from tools that vary in capitalization. Ignore blank lines stops empty rows inflating your totals. Every panel and every count recomputes the instant you toggle an option, so set the comparison rules first, then trust the numbers the tool reports.
Read the four result panels for different jobs
Merge + dedupe gives the clean union, every distinct item once, in first-seen order, which is the export you usually want. Merge all keeps every row including repeats, useful when frequency itself is the signal. Duplicates across lists shows only items present in two or more lists, with a count of how many lists and how many times each appears. Unique to each isolates the items that belong to a single list, the fastest way to see what one source has that the others do not.
Apply it to keyword, backlink, and domain reconciliation
List comparison is constant, low-glamour SEO work. Merge two keyword exports and dedupe to build a single master sheet without double-counting. Drop three backlink exports into separate lists and read Duplicates across lists to find the links every source agrees on. Paste a prospecting list and a do-not-contact list, then use Unique to each to see only the safe targets. Because membership is counted per distinct list, an item repeated inside one list never falsely registers as cross-list overlap.
Merge lists and duplicate finder frequently asked questions
Q1What is the difference between merge, dedupe, and finding duplicates?
Merge all stacks every item from every list together and keeps repeats. Merge + dedupe collapses that into the union, each distinct item once. Finding duplicates is different again: it reports only the items that appear in two or more separate lists, which is the overlap between your sources rather than repetition within a single list.
Q2Does case-insensitive matching change my results?
Yes, often significantly. With case-insensitive on, Example.com and example.com are treated as one item, so they collapse in the union and can register as a cross-list match. Turn it off and the two are counted separately. Set this option to match how your source tools format text, then read the counts, because the comparison rule directly drives every number shown.
Q3How does it count an item that repeats inside one list?
Cross-list membership is counted once per list. If a single list contains the same item three times, that list still contributes only one to the item’s list count, so a within-list repeat never inflates the across-lists result. The Merge all panel and the occurrence count do still show the raw repeats when you need to see frequency.
Q4Is there a limit on how many lists or items I can compare?
You can add up to eight lists with the Add button and remove any down to a minimum of two. There is no fixed cap on items per list beyond what your browser handles comfortably; the tool runs locally, so large pastes stay fast and private. For very large datasets, expect performance to track your device rather than any server limit.
Q5Is my pasted data sent anywhere?
No. Every calculation runs in your browser with client-side JavaScript. Nothing you paste into the lists is uploaded, logged, or stored, and the tool keeps working offline once the page has loaded. That makes it safe for confidential keyword lists, private backlink exports, or any data you would not want leaving your machine.
