Substitution Cipher (Keyword Alphabet)
Security ToolsSwap every letter using a keyword or custom alphabet
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All history →Substitution Cipher (Keyword Alphabet) — at a glance
Swap each letter for another using your own alphabet.
How to use it — step by step
Your text and a key: a keyword like ZEBRAS, or 26 different letters.
Add your text
Paste or type your input into the box. The Sample button fills in an example.
Choose the options
Pick the mode and settings you need. Results update when you run the tool again.
Press Run Cipher
The result is made instantly inside your browser.
Copy the result
Use the Copy button, or send it to another tool.
Pro tips
Small things that make the result better.
Quick facts
Frequently Asked Questions
How is the alphabet made from a keyword?+
Repeated letters are dropped, then the unused letters follow in order. ZEBRAS gives ZEBRASCDFGHIJKLMNOPQTUVWXY.
Is it secure?+
No. It is good for puzzles and learning only.
Is my data safe?+
Yes. Everything runs inside your own browser. Your text, files and images are never uploaded to any server.
Is this tool really free?+
Yes — completely free, no signup, no watermark and no usage limit.