What is the pigpen cipher?

The pigpen cipher, also called the Masonic or Freemason cipher, is a geometric substitution cipher that replaces each letter with a fragment of a grid. It was used by Freemasons in the 18th century to keep records private and appears in many puzzles and games.

How are the symbols assigned?

Letters are placed into two tic-tac-toe grids and two large X (saltire) grids. Each letter takes the shape of the lines surrounding its cell. In the common scheme the second tic-tac-toe grid and the second X grid add a dot inside the same shapes, doubling the available symbols to cover all 26 letters.

Is the pigpen cipher secure?

No. It is a simple monoalphabetic substitution, so it preserves letter frequencies and is broken with basic frequency analysis just like a Caesar cipher. Its value today is decorative, educational and recreational, not for real secrecy.

Why does the tool use box-drawing characters?

True pigpen glyphs are line drawings, so this tool approximates each cell's shape with Unicode box-drawing characters and an added dot where the scheme requires one. This keeps the output as plain copyable text while still showing the distinct corner, edge and X shapes.

What happens to spaces and numbers?

Spaces, digits and punctuation are not part of the pigpen alphabet, so they pass through unchanged in both directions. Only the 26 letters A-Z are substituted with symbols.

Pigpen Cipher — Gera Tools

The pigpen cipher — also known as the Masonic or Freemason cipher — is a geometric substitution cipher that replaces each letter with a small drawing. Instead of shifting the alphabet, it arranges the letters into grids and gives each letter the shape of the lines that surround its cell. Freemasons used it in the 1700s to keep their records private, and it remains popular in puzzles, escape rooms and children’s secret-message games.

How it works

The 26 letters are split across four grids:

A tic-tac-toe grid holds the first nine letters (A–I); each letter’s symbol is the corner or edge shape of its cell.
A second tic-tac-toe grid holds J–R using the same shapes plus a dot inside.
An X-shaped (saltire) grid holds S–V as the four wedges of the X.
A second X grid holds W–Z using the same wedges with a dot.

Because each cell has a unique combination of surrounding lines, every letter gets a distinct symbol, and the dot variants double the symbol set so all 26 letters fit. This tool renders those shapes with Unicode box-drawing characters (adding a centre dot where the scheme requires one) so the output stays as plain, copyable text. Decoding simply reverses the lookup.

Worked example

Encoding the word FREEMASON substitutes each letter for its grid symbol. The two Es produce the same symbol because pigpen is monoalphabetic — a single letter always maps to a single shape. Decoding the same string of symbols restores FREEMASON exactly, with any spaces or punctuation left untouched.

Notes and tips

Pigpen offers no real security: it is a one-to-one substitution, so repeated letters give it away and frequency analysis breaks it instantly. Treat it as a fun, visual cipher rather than a protective one. Letters are case-insensitive on encode and return as upper case on decode; spaces, digits and punctuation pass straight through. All encoding and decoding happen locally in your browser.