Felo

Made Up Language Translator Online – Letter Substitution Cipher

Convert English text into a made-up language by swapping every letter with the page's fixed letter-or-digraph cipher, or decode substituted text back to English. Case is preserved, punctuation and digits stay untouched, and every result is returned as copyable text. Try it online.

What is Made Up Language Translator Online – Letter Substitution Cipher?

This agent applies a fixed letter-substitution cipher to English text. Each Latin letter is swapped for a different letter, and two letters (m and y) become two-letter digraphs, so the result looks like a playful invented language. The same mapping runs in reverse, so text produced by the cipher can be turned back into English. It is a cipher, not a real language: there is no grammar, vocabulary, or pronunciation behind it.

Key Features

Complete 52-character mapping. Lowercase and uppercase letters each have their own substitution, including the digraphs qu for m/M and ch for y/Y.
Two directions. Ask to encode English into the made-up language, or decode substituted text back into English.
Exact preservation. Spaces, punctuation, digits, emoji, and line breaks pass through unchanged; nothing is silently dropped.
Round-trip checking. After encoding, the agent can verify that decoding the result returns your original text.
Copyable output blocks. Results arrive as plain text you can copy, including multi-line passages handled line by line.

How to Use

Paste the text you want to convert and say which direction you want, for example "encode this" or "decode this". If you do not say, the agent infers the direction from the text and states its assumption.
Read the converted text in the code block. For long passages, the agent keeps your line breaks so you can match lines up.
Ask for the reverse direction on any result to check it, or request a second passage in the same conversation without repeating the rules.

Example Use Cases

Writing a made-up language message for a game or story. Encode a short line like "meet me at the old bridge" and get a cipher line you can paste into a note or puzzle.
Decoding a made-up language translator output. Paste substituted text such as "quooh quo uh hto epx zkxvvo" and ask for the English behind it.
Making a letter substitution cipher worksheet. Encode a list of words line by line, keep the answers, and use the decode direction to check them.

Tips for Best Results

State the direction when the text is ambiguous; a short encoded word can look like an English word.
Keep the original text handy if you plan to decode later, since the cipher is fixed and reversible but easy to mix up by hand.
Ask for line-by-line output when you are converting a list, so each result stays aligned with its source.

FAQ

What input does it accept?
Plain text of any length you can paste. Letters are converted; spaces, punctuation, numbers, and symbols are preserved as-is. Very long passages are handled in sections so nothing is cut off.

How accurate is the result?
The mapping is deterministic, so the same input always gives the same output. Accuracy depends on direction: encoding is exact, and decoding works when the text was produced with this same mapping. Text from a different cipher will not decode correctly, and the agent will say so rather than guess.

How is this different from some free text tools?
Some free text tools show two boxes and leave the direction and character handling unexplained. This agent states the direction it used, preserves unsupported characters instead of dropping them, and can run the reverse direction on its own output so you can confirm the round trip.

Is this a real language?
No. It is a letter substitution cipher with no vocabulary or grammar. It will not translate meaning into another language, and it does not produce audio or fonts.