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Merge Lists

Free online list merger. Combine two lists by concatenating, interleaving, union (all unique items), or intersection (common items only). Remove duplicates and sort the result. No signup required.

Mode:
0List A
0List B
0Output
0Dupes rm
List A
List B
Result

Options

How to merge two lists

  1. Paste List A into the first column — one item per line.
  2. Paste List B into the second column — one item per line.
  3. Choose a merge mode — Concat, Interleave, Union, or Intersection. The result updates instantly in the third column.
  4. Adjust options — remove duplicates, sort the result, or enable case-sensitive matching.
  5. Copy the result with the copy button above the output column.

Merge modes explained

Concatenate

A=[1,2,3] + B=[4,5] → [1,2,3,4,5]

Appends all items from List B after all items from List A. The simplest merge — use it when you want to combine two exports into one sequential list.

Interleave

A=[1,2,3] + B=[a,b] → [1,a,2,b,3]

Alternates items from A and B: A₁, B₁, A₂, B₂, … When lists are unequal lengths, the remaining items from the longer list are appended at the end. Use for balanced queues, alternating question sets, or round-robin ordering.

Union

A=[1,2,3] + B=[2,3,4] → [1,2,3,4]

Returns all unique items from both lists — equivalent to SQL UNION. Items that appear in both lists are included once (from List A). New items from List B are appended in order. Use to combine two tag lists, keyword sets, or email lists without duplicates.

Intersection

A=[1,2,3] + B=[2,3,4] → [2,3]

Returns only items that appear in both lists — equivalent to SQL INNER JOIN / set intersection. Use to find common emails between two lists, shared tags between two posts, or overlapping inventory between two datasets.

Common use cases

Combine two exports

Merge two CSV column exports or data dumps into one list before importing into a spreadsheet or database.

Find email overlap

Use Intersection to find addresses on two mailing lists — subscribers who signed up through two different channels.

Deduplicate after merge

Concatenate two keyword lists then enable Remove duplicates — faster than doing it manually in a spreadsheet.

Round-robin scheduling

Interleave two teams or task queues to create a fair alternating assignment order.

Tag reconciliation

Use Union to get a master list of all unique tags across two content sets, or Intersection to find shared tags.

A/B list comparison

Paste the same list at two points in time — use Intersection to find what survived, use Union minus Intersection to find what changed.

Frequently Asked Questions

What is the difference between the merge modes?

Concatenate appends List B after List A. Interleave alternates items (A1, B1, A2, B2, …). Union returns all unique items from both lists — like a SQL UNION. Intersection returns only items that appear in both lists — like a SQL INNER JOIN.

How do I remove duplicates when merging?

Enable the "Remove duplicates" toggle in options. For Concatenate mode, duplicates are removed after merging. Union mode already deduplicates by definition. Intersection mode returns each common item only once.

What does Interleave do with unequal list lengths?

When List A and List B have different lengths, interleave continues with the remaining items from the longer list after the shorter one runs out. For example, A=[1,2,3] and B=[x] gives 1, x, 2, 3.

Is the comparison case-sensitive?

No — by default "Apple" and "apple" are treated as the same item for duplicate removal, union, and intersection. Enable Case-sensitive if you need exact character matching.

Can I sort the merged result?

Yes. Enable the "Sort result" toggle to sort the output alphabetically after merging. This is useful when combining two sorted lists that need to remain sorted after the merge.

What is a practical use for each merge mode?

Concatenate: combine two exports into one list. Interleave: alternate questions from two sets for a balanced quiz. Union: find all unique tags across two blog posts. Intersection: find emails on two mailing lists to identify overlap.

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