ROT13 Encoder
Use the CaseSwitch ROT13 Encoder & Decoder to rotate A–M with N–Z (and back). Paste the text, copy the result — applying ROT13 twice restores the original. Processing stays in this browser. It is spoiler obfuscation, not encryption.
Written by the CaseSwitch editorial team. We maintain these tools in the browser so drafts, keys, and images stay on your device.
Last reviewed: 23 July 2026
Processed locally in your browser. Nothing is sent to a server.
Paste or type text to convert. Output stays empty until there is input.
Character count: 0 · Word count: 0 · Line count: 0
Examples
Encode Hello
Input
Hello
Output
Uryyb
Decode Uryyb
Input
Uryyb
Output
Hello
Encode CaseSwitch
Input
CaseSwitch
Output
PnfrFjvgpu
Full alphabet round identity
Input
NOPQRSTUVWXYZABCDEFGHIJKLM
Output
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Spoilers with punctuation
Input
Spoilers ahead!
Output
Fcbvyref nurnq!
How to use
- Paste the text into the input panel.
- Copy the ROT13 output.
- Paste the output again to recover the original — same button either way.
What this tool is for
ROT13 is a Caesar shift of 13. Forums used it for spoilers because one function both hides and reveals English letters. Digits and punctuation stay. It is not confidentiality — anyone can rotate it back instantly.
How it works
Each English letter is shifted 13 within its case. The same transform encodes and decodes. Non-letters are unchanged. There is no separate key beyond “use ROT13.”
When to use it
Hiding movie endings in a forum post, classic Usenet-style spoilers, classroom demos of symmetric trivial ciphers, and quick round-trips to show self-inverse behavior.
When not to use it
Anything confidential. PII. Exam answers you need to actually protect. Prefer real crypto and access control for secrets.
How it compares to related tools
Caesar Cipher with shift 13 is the same idea with an explicit shift control. Inverse Case flips case, not alphabet position. Base64 is encoding, still reversible.
Common mistakes
ROT13-ing a password and storing it. Expecting numbers to change (they do not). Thinking obscurity equals security.
Why 13?
The English alphabet has 26 letters, so a shift of 13 is its own inverse. One function both “encodes” and “decodes,” which is why forums loved it for spoilers.
What does not rotate
Digits, spaces, and punctuation stay the same. Only A–Z and a–z move. That keeps sentence shape readable while hiding words.
Frequently asked questions
Why 13?+
The English alphabet has 26 letters, so one function both encodes and decodes.
Does ROT13 work on numbers and punctuation?+
They are unchanged. Only A–Z/a–z rotate.
Is ROT13 encryption?+
No. It is trivial obfuscation. Anyone can reverse it in one click.
How is this different from Caesar?+
ROT13 is Caesar locked to shift 13. The Caesar tool lets you pick other shifts.
Will applying it twice restore the text?+
Yes for English letters. That is the usual spoiler workflow.
Is my text uploaded?+
No. Conversion runs in this browser.
Does this tool send my payload to CaseSwitch?+
No. Formatting, encoding, and naming conversions for this page run in your browser after load — your sample stays on the device.
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