Duplicate List - Create Multiple Copies of a List Online

What Is a List Duplicator?

The Duplicate List tool lets you create multiple copies of each item in a list. You can repeat each item a specified number of times, arranged either sequentially (all copies of item A, then all copies of item B) or alternating (one copy of each item, repeated). This is useful for testing, generating templates, creating mock data, and more.

Split your input list by a character or regular expression, choose how many copies to make, select the arrangement pattern, and pick an output separator for the final result.

How to Duplicate a List

Paste or type your list into the Input List text area.
Choose a Separator Mode — use Literal for a fixed character or Regex for a pattern.
Enter the Input Separator that currently divides your items.
Set the Number of Copies for each item.
Choose Sequential (AAA, BBB) or Alternating (ABC, ABC) arrangement.
Set the Output Separator and view the duplicated list instantly.

Common Use Cases

Generate repeated test data for software development and QA testing.
Create templates where each item needs to appear multiple times.
Build patterns for data entry or batch processing workflows.
Generate sample datasets for demonstrations or training materials.

Frequently Asked Questions

What is the difference between Sequential and Alternating arrangement?

Sequential arrangement duplicates each item fully before moving to the next (e.g., A, A, A, B, B, B). Alternating arrangement cycles through all items one at a time (e.g., A, B, C, A, B, C).

What is the maximum number of copies I can make?

You can make up to 1,000 copies per item. However, please note that very large outputs may affect browser performance.

Can I use a regular expression as a separator?

Yes. Switch to Separate by Regex mode and enter a valid regex pattern. For example, \s+ splits on any whitespace.

Is my list data sent to a server?

No. All processing is done entirely in your browser. Your list data never leaves your device.