Duplicate List
Duplicate a list - repeat the whole list or each item N times. Newline / comma / tab / pipe / space separators. Free, offline, client-side, instant, secure.
Repeat your entire list N times, or repeat each item N times in place.
Six separators, live output, stats, and Ctrl/Cmd + Enter to re-run.
How to Use Duplicate List
- Paste your list in the input textarea.
- Pick the separator that matches your input (newline, comma, semicolon, tab, pipe, or space). The same separator is used for the output.
- Pick the mode. "Repeat whole list" produces
A, B, C, A, B, C(the whole list N times). "Repeat each item" producesA, A, B, B, C, C(each item N times in place). - Set the count (1-10,000). Output updates live as you type; counts above 1,000 trigger a non-blocking info toast.
- Copy or download the result. Ctrl/Cmd + Enter re-runs explicitly.
Frequently Asked Questions
What’s the difference between the two modes?
“Repeat whole list” treats the entire input as one block and concatenates N copies of it. “Repeat each item” walks the list once and emits each item N times before moving on. So for input A, B, C with N = 3: whole-list mode produces A, B, C, A, B, C, A, B, C; each-item mode produces A, A, A, B, B, B, C, C, C.
Don’t both modes have the same total item count?
Yes – both produce exactly (original_count × N) items in total. The two modes only differ in interleaving order, not in how many items end up in the output. An earlier version of this FAQ stated both formulas separately as if they were different – they aren’t; the wording was confusing. Stats line now shows the same total regardless of mode.
How does the separator selection work?
The chosen separator is used to split the input into items and then to join the duplicated items back into a string. So if your input is comma-separated, set the separator to comma; the output will also be comma-separated. Six common separators are supported: newline, comma, semicolon, tab, pipe, and space.
What’s the maximum count?
10,000. The tool will allow any value in 1-10,000. Above 1,000 a non-blocking info toast tells you the operation may take a moment; the result still renders. A 50,000-item input × 10 repeats produces 500,000 items and runs in well under a second on a modern machine.
Can I use a custom separator that isn’t in the dropdown?
Not directly. Workaround: find-and-replace your custom separator with one of the six supported ones (in any text editor) before pasting, then duplicate, then convert back if needed. Adding a free-form separator field is a likely future tweak; the trade-off is escaping rules – e.g. allowing “||” as a separator means we have to decide what “|” means in items.
Does count = 1 do anything?
It produces output identical to the input (split + immediate rejoin with the same separator, no duplication). Useful as a sanity check that your separator setting is correct.
What format is the download?
Plain UTF-8 text (.txt), filename duplicated-list.txt. Opens cleanly in spreadsheets, text editors, programming tools, and databases.
Is anything sent to a server?
No. The page loads three static files (HTML, CSS, JS) and then runs entirely in your browser. You can disconnect from the internet after the page loads. No analytics, no tracking, no cookies.
Is this tool free?
Yes – free, unlimited, no signup, no watermark. Use the output in any context. Attribution to is appreciated but not required.