How to use the Vigenere Cipher Converter
Enter text, choose a mode, and check the result below the controls. The repeating Keyword shifts letters while the converter keeps their case. Spaces, digits, punctuation, and other characters outside A-Z and a-z stay in place and do not use a keyword position.
Encrypt or decrypt text with a keyword
- Choose Encrypt or Decrypt under Cipher mode.
- Review Keyword, which starts with
KEY, and replace it when needed. - Type or paste content into Input text. The read-only result appears when both fields contain usable values.
- Use Upload to open a picker marked for
.txtandtext/plainfiles. - Use Copy or Download .txt below the result. Downloads use
vigenere-cipher-output.txt.
What the Vigenere keyword changes
The converter removes every character outside A-Z and a-z from Keyword, then uses the remaining letters without regard to case. A non-empty value with no letters shows Keyword needs at least one letter (A-Z). and leaves the output empty. An empty value clears the output without showing that message.
For decryption, enter the same keyword used for encryption and choose Decrypt. A different keyword produces different shifts.
Vigenere cipher encryption and decryption examples
Keyword letters repeat across the eligible letters in Input text. Encrypt shifts forward through the alphabet, while Decrypt shifts backward. The shift wraps at Z, and the original case remains in place.
Input text: ATTACKATDAWN
Keyword: LEMON
Cipher mode: Encrypt
Output: LXFOPVEFRNHRIn a mixed string, punctuation and spaces remain where they were. They do not consume a keyword letter, so the next alphabetic character continues the repeating sequence.
Input text: Hello, World!
Keyword: KEY
Output: Rijvs, Uyvjn!Check preserved characters in the result
Use mixed-case text when you need to inspect case handling. The output keeps uppercase and lowercase positions while transforming only A-Z and a-z.
Include commas, numbers, spaces, or symbols to see them pass through unchanged. Because these characters do not advance the keyword, the key sequence continues at the next letter.
When another text converter fits better
Choose the Vigenere Cipher Converter when a repeating keyword should control the letter shifts. For one fixed shift or the ROT13 preset, use the Caesar Cipher Converter. For Base64 encoding or decoding, use the Base64 Encoder / Decoder. The parent Text Conversion Tools category lists these and other text representations.
The conversion code runs in browser JavaScript. This page's code contains no fetch, XMLHttpRequest, sendBeacon, or form post that sends the entered text.
Frequently asked questions
How do I decrypt Vigenere text?
Choose Decrypt and enter the exact keyword used for encryption. The converter shifts eligible letters backward while preserving case and non-letter characters.
Does Vigenere conversion preserve spaces and punctuation?
Yes, spaces, punctuation, digits, and other non-A-Z/a-z characters remain unchanged. They also do not advance the repeating keyword.
What happens if my Keyword has numbers or symbols?
Numbers, spaces, and punctuation are removed from Keyword, and the remaining letters are used case-insensitively. If no letters remain in a non-empty value, the tool shows Keyword needs at least one letter (A-Z).
Is Vigenere conversion done in my browser?
Yes. The conversion code runs in browser JavaScript, and this page's code contains no fetch, XMLHttpRequest, sendBeacon, or form post that sends the entered text.