happytails.ai

Vigenère cipher encoder and decoder

Open Vigenère cipher encoder and decoder on Happytails.ai. This view has the same page content and links, with explicit tool capabilities. Read the processing notes before using a tool.

Tool capabilities

{
  "id": "vigenere-cipher",
  "category": "text-tools",
  "built": true,
  "requirements": "Repeats a letter key over A–Z; spaces and punctuation do not advance the key. For puzzles and learning only. It is not secure encryption.",
  "implementation": {
    "fields": [
      {
        "key": "key",
        "label": "Key (letters A–Z)",
        "value": "LEMON",
        "type": "text"
      },
      {
        "key": "direction",
        "label": "Direction",
        "value": "Encode",
        "type": "select",
        "values": [
          "Encode",
          "Decode"
        ]
      }
    ],
    "live": true,
    "note": "Repeats a letter key over A–Z; spaces and punctuation do not advance the key. For puzzles and learning only. It is not secure encryption.",
    "experience": {
      "automatic": true,
      "single": false,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Your text",
      "placeholder": "Type or paste your input…",
      "help": "Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.",
      "helpParts": [
        "Change the input or settings to update your result.",
        "Results update as you type.",
        "Up to 1,000,000 characters."
      ],
      "action": null
    },
    "mode": "automatic",
    "interactive": false
  },
  "execution": "Browser interface",
  "api": null,
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}

Page guide

Make a repeating-key letter cipher for a puzzle or lesson.

How to use Vigenère cipher encoder and decoder
  1. Enter your message, a key containing letters A–Z, and choose Encode or Decode. The key repeats across letters only; spaces and punctuation do not consume a key character.
  2. ATTACK AT DAWN with key LEMON becomes LXFOPV EF RNHR. Choose Decode with the same key to restore it.

Useful next steps

Caesar cipher encoder and decoderMorse code translatorUppercase

How to use it

Enter your message, a key containing letters A–Z, and choose Encode or Decode. The key repeats across letters only; spaces and punctuation do not consume a key character.

Try a small example

ATTACK AT DAWN with key LEMON becomes LXFOPV EF RNHR. Choose Decode with the same key to restore it.

What to know

Repeats a letter key over A–Z; spaces and punctuation do not advance the key. For puzzles and learning only. It is not secure encryption.