List Duplicate

It takes a list of items and creates multiple copies of them. You can arrange copies by appending them after the original (concatenate) or alternating each item with its copies (interweave).

Paste or type your list items, choose a separator (comma, newline, space, semicolon, or tab), set the number of copies, pick a mode, and click Duplicate.

Concatenate mode appends all copies after the original list. For example, [A, B] with 3 copies becomes [A, B, A, B, A, B].

Interweave mode groups each item with its copies. For example, [A, B] with 2 copies becomes [A, A, B, B].

You can split input by comma, newline, space, semicolon, or tab. Output can be joined with any of the same separators.

Yes. All processing happens locally in your browser. No data is sent to any server, and no registration is required.

Yes, the List Duplicate tool is completely free with no usage limits or hidden fees.

Yes. The tool runs entirely in your browser using JavaScript, so it handles large lists efficiently without uploading anything.

Use it to generate test data, create repeated patterns, build CSV rows, prepare bulk text entries, or multiply items for data processing tasks.

Yes. The tool is fully responsive and works on desktop, tablet, and mobile browsers.

You can set up to 100 copies per item, which is sufficient for most list duplication needs.

Yes. You can choose a different separator for input splitting and output joining independently.