ROT13 Encoder and Decoder

This ROT13 encoder and decoder shifts every letter 13 places, which hides spoilers and puzzle answers. Running it twice gives back the original. Caesar shifts, ROT5, ROT18, and ROT47 are included too.

Updated
Runs in your browser. Your text is not uploaded.

ROT13, ROT5, ROT18, and ROT47 undo themselves: run the output through again to get the original back.

Result 

    

    


    

    

                                                
        

                    

            
How to use the ROT13 Encoder / Decoder

        
  1. Type or paste your text.
  2. Pick ROT13, a Caesar shift, ROT5, ROT18, or ROT47.
  3. Copy the result, or press Use as input to run it through again.



                    

            
How it works

        
Each letter moves forward in the alphabet by the shift, wrapping from Z back to A:
encoded = (letter + shift) mod 26
With a shift of 13, going forward 13 twice brings you back to the start, so the same operation encodes and decodes. ROT5 does the same for digits with a shift of 5 out of 10. ROT47 shifts all 94 printable ASCII characters from ! to ~ by 47, so punctuation and digits change too.



                    

            
Examples

        
  • Hello = Uryyb (ROT13).
  • Uryyb = Hello (ROT13 again).
  • abc with a Caesar shift of 3 = def.
  • Hello = w6==@ (ROT47).



                    

            
ROT13 alphabet

        
PlainROT13
A B C D E F G H I J K L MN O P Q R S T U V W X Y Z
N O P Q R S T U V W X Y ZA B C D E F G H I J K L M



                    

            
ROT13 is not encryption

        
ROT13 hides text from a casual glance, which is why forums used it for spoilers and joke punchlines. It gives no security: there are only 25 possible shifts, and anyone can try them all in seconds. Use real encryption for anything private.
Julius Caesar is said to have used a shift of 3 for military messages, which is where the name Caesar cipher comes from.



                    

            
Limitations

        
  • Only the 26 Latin letters are shifted in ROT13 and Caesar mode; accented letters stay as they are.
  • Not encryption. Anyone can reverse it.



            

        

        
Frequently asked questions

        

                            

                    How do I decode ROT13?

                    
Apply ROT13 again. Because 13 + 13 = 26, the second shift brings every letter back.

                

                            

                    What is the difference between ROT13 and a Caesar cipher?

                    
ROT13 is a Caesar cipher with a fixed shift of 13. A Caesar cipher can use any shift from 1 to 25.

                

                            

                    What does ROT47 change?

                    
All printable ASCII characters, including digits and punctuation, not just letters.

                

                    

    

        

        

            
            
Often used together with the ROT13 Encoder / Decoder.