Random alphabet
Create a substitution alphabet to encode or decode a message.
Generate a coded alphabet, fill in a custom table, or progressively rebuild the mappings of an encrypted message.
Source text
Result
Substitution alphabet
Encoding table
Substitution alphabet
Plain alphabet : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Coded alphabet : __________________________
Available letters
Substitution alphabet
Plain alphabet : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Coded alphabet : __________________________
Decoding table
Available letters
Quick explanation
In Encode mode, each plain letter is replaced by the letter shown in the coded alphabet. In Decode mode, enter the mappings you know: letters that are still unknown remain marked with _.
Try this too
Need a reversed alphabet?
Atbash directly applies the A ↔ Z, B ↔ Y substitution without a custom table.
Additional information
Understanding substitution alphabets
A random alphabet is a monoalphabetic substitution cipher: every plain alphabet letter is replaced by another letter. The rule stays the same throughout the message. If A is replaced by Q, every A in the text becomes Q during encoding.
This is useful for riddles, treasure hunts, and simple coded messages. It is not modern secure encryption: with clues, letter frequencies, or likely words, an experienced solver can often break it.
Automatic encoding
Automatic mode shuffles the 26 letters and creates a complete key in one click. Copy the coded alphabet if you want to save it or share it with the person who will decode the message.
Manual encoding
Manual mode lets you build your own coded alphabet. Available letters show which letters have not been used yet, helping you avoid entering the same substitution twice.
Decoding by guesses
In decode mode, fill the table with the mappings you have found. Unsolved letters remain displayed as _, so you can track progress without losing the shape of the message.
Reading the mapping table
| Plain alphabet | A | B | C | D |
|---|---|---|---|---|
| Coded alphabet | Q | M | Z | R |
| Effect | A becomes Q | B becomes M | C becomes Z | D becomes R |
With this table, the word CAB becomes ZQM. To decode, apply the mapping in the other direction: Q becomes A again, M becomes B, and Z becomes C.
Tips for solving a message
Start by looking for frequent letters, short words, and repeated patterns. In English, words such as THE, AND, TO, or OF often provide useful clues. Enter a guess in the decoding table, check the result, then adjust if the text does not look plausible.
Accented letters are converted to their plain A-Z equivalents. Punctuation, spaces, and digits are preserved so the rhythm of the original message remains visible.
Which substitution tool should you choose?
| Tool | Main strength | Best use |
|---|---|---|
| Alphabet checker | The most minimal one. | Use it to quickly test a 26-letter line you have found, copied, or received. |
| Random alphabet | The most powerful for generating and solving. | Use it to generate an encoding alphabet, fill a table manually, or work calmly through a coded message. |
| Simple substitution | The most ergonomic for building a key manually. | Use it to place letter tiles one by one, avoid duplicates, and correct a substitution easily. |
Limits and reuse
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