Create a Symmetric List
Create a palindromic list from the given list. Runs entirely in your browser, so your data never leaves your device.
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Output
The result appears here as you type.
How to use Create a Symmetric List
- 1. Paste your list. Enter your items into the input pane, one per line. Any list you want mirrored into a palindrome-style sequence works here.
- 2. Decide how to handle the middle item. Turn on Don't repeat the middle item so the last item of your original list appears only once in the center, instead of being duplicated at the point of symmetry.
- 3. Copy the symmetric list. The output pane shows your list followed by its reverse, forming a mirrored, palindromic sequence. Copy the result wherever a symmetric list is needed.
When to use Create a Symmetric List
Create a Symmetric List mirrors a list by appending its reverse, producing a palindromic sequence. It is for situations where a list needs to read the same forward and backward, centered on the original last item.
- Generating a bounce animation sequence. A list of animation frame names needs to play forward then backward to create a bounce effect, and mirroring the list produces that full back-and-forth sequence.
- Building a symmetric color gradient. A list of color stops needs to fade in and then fade back out symmetrically, and mirroring the sequence gives you the reversed second half automatically.
- Creating a palindrome puzzle from list items. You are building a word or pattern puzzle that requires a sequence reading the same forward and backward, and mirroring a base list is the fastest way to produce one.
- Avoiding a doubled center in a mirrored list. When the last item of the original list would otherwise appear twice in the middle of the mirrored result, turning off the repeat keeps the sequence properly symmetric.
Examples
Mirror a list
Input
a b c
Output
a b c c b a
About the Create a Symmetric List tool
Create a Symmetric List runs as plain JavaScript in your browser tab, with no server behind it. Create a palindromic list from the given list. Whatever you put in stays on your device from start to finish.
The tool is part of EditSafely's List Tools section, 114 single-purpose utilities built around the same idea: open the page, get the result, keep your data to yourself.
You can shape the output with the Don't repeat the middle item setting, and the result refreshes the moment you change it. A worked example further down the page shows exactly what the tool produces for a real input.
That local-first design has practical benefits beyond privacy. The tool keeps working on a flaky connection once the page has loaded, results are instant because nothing round-trips to a server, and it is safe to use with confidential material.
Frequently asked questions
Does Create a Symmetric List cost anything?
Yes, it is completely free. All 2,658 tools on EditSafely work without an account, a subscription or usage limits.
Is it safe to paste sensitive or confidential data?
No data leaves your device. The whole tool is JavaScript that runs inside your browser tab, so there is no upload, no server-side processing and no log of what you did. If you disconnect from the internet after the page loads, it keeps working.
How much text can I process at once?
There is no fixed limit. Because the work happens on your own device rather than on a shared server, the practical ceiling is your machine's memory, which comfortably handles inputs far larger than typical online tools allow.
Do I need to sign up or install anything?
Nothing to install and no account needed. Open the page in any up-to-date browser, including on a phone or tablet, and the tool is ready.
How do I use the result?
The output panel has a one-click copy button, and you can keep refining the input while you work; the result updates in place as you type.