ROT13 Encoder Decoder
Convert text to and from ROT13 instantly. ROT13 is a Caesar cipher with a fixed shift of 13, so the same action both encodes and decodes. Useful for hiding spoilers, puzzle answers, and quick reversible obfuscation.
Free, instant, and private — everything runs right in your browser.
Example usage
Example input
Hello, World!
Example output
Uryyb, Jbeyq!
Batch Processing
Enter multiple inputs, one per line. Each line will be processed separately.
Why this tool?
Everything runs right in your browser — no uploads, no sign-up, no waiting. Your text never leaves your device.
Quick tips
- •Outputs update live as you type.
- •Use the sticky copy button to grab results quickly.
- •Bookmark this page for fast access.
More like this
Discover related tools and step-by-step guides for this kind of task.
How it works
- Paste the text you want to convert.
- Each letter is rotated 13 places through the alphabet.
- Run ROT13 again on the result to get back the original text.
Use cases
The internet’s spoiler curtain
ROT13 became a convention on Usenet in the early 1980s, and its job was never security — it was consent. Posting a punchline, a spoiler, or an offensive joke in ROT13 meant a reader had to actively choose to decode it. Newsreaders added a single keystroke to flip the text, making the barrier deliberate but trivial. The same idea survives today in puzzle forums and subreddits.
The elegance is mathematical: the Latin alphabet has 26 letters, and 13 is exactly half. Rotate by 13 and you land halfway round; rotate again and you return to where you started. That makes ROT13 its own inverse — one operation both encodes and decodes, which is why this tool needs no mode switch.
Quirks worth knowing
A handful of English words map onto other real words under ROT13, which programmers have collected for decades: "purely" becomes "cheryl", "abjurer" becomes "nowhere", and — the most famous — "PNG" becomes "CAT". The letters n and a swap, as do e and r, which is why short words flip so readily.
Because ROT13 is a Caesar cipher with a fixed shift, our Caesar Cipher tool covers every other rotation if a puzzle uses a different key. And it bears repeating: ROT13 offers zero protection. It is a curtain, not a lock — appropriate for spoilers and jokes, never for anything that matters.
Encoding
Explore all encoding and decoding tools
Browse every tool for this kind of task, along with helpful guides that show you how to get the most out of them.
Related tools
Supporting guides
Conversion History
Loading...
FAQ
What is ROT13?
ROT13 is a special Caesar cipher that shifts every letter 13 positions. Because the alphabet has 26 letters, applying ROT13 twice returns the original text.
How do I decode ROT13?
Just run ROT13 on the encoded text again. The same operation both encodes and decodes, so no separate decode mode is needed.
Is ROT13 secure?
No. ROT13 is meant for casual obfuscation like hiding spoilers, not for real security. Anyone can decode it instantly.