Simple substitution
Build a substitution alphabet with letter tiles.
Progressively map each source letter to a substitution letter and watch the result fill in live.
Source text
Result
Substitution alphabet
Select a tile, then a cell.
Mappings
Available letters
Quick explanation
Select an available letter, then an alphabet cell. Unmapped letters remain displayed as underscores.
Try this too
Need a generated alphabet?
Use Random alphabet to automatically create a complete substitution alphabet.
Additional information
How does simple substitution work?
A simple substitution replaces each source letter with another letter. Here, you build the alphabet manually with tiles: a letter cannot be used twice, which prevents inconsistent alphabets.
Cells and tiles
Select an available tile, then a cell. If the cell already contains a letter, the previous letter returns to the available tiles.
Swaps
Select a filled cell, then another filled cell to swap their substitutions. This lets you fix an alphabet without starting over.
Progressive result
Unmapped letters become _. Spaces, digits, and punctuation stay visible so the message structure remains readable.
Example
If A → M and E → T, the word Ace becomes M_t until the other letters are mapped. To compare with a generated alphabet, also use Random alphabet.
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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