Pigpen Cipher — Full Reference Chart

Pigpen cipher substitutes every letter of the alphabet with its own geometric symbol derived from its position inside one of four reference grids, rather than with another letter, number, or sound. It's visually distinctive enough that most people recognize the symbols on sight even without knowing what they mean, which has made it a fixture in escape rooms, puzzle books and Masonic-themed fiction, well beyond its original, more limited historical use.

Records Go Back Further Than the Freemason Association Suggests

Despite its common nickname, pigpen isn't a Masonic invention from a clean, single point of origin. Grid-based substitution systems resembling it are documented at least as far back as the 18th century, and some historical accounts trace grid-and-dot letter concealment even earlier, with claims — of varying reliability — connecting related ideas to Hebrew rabbinical writing traditions and to the Knights Templar during the medieval Crusades. What's more solidly documented is that English Freemasons had adopted and standardized a specific four-grid version of the cipher by around 1737, using it informally within lodge correspondence, which is the direct reason the system carries the Freemason's name today even though its underlying grid-substitution concept almost certainly predates any one fraternal order's use of it.

The Four Grids, Explained Cell by Cell

The standard version most commonly taught splits the alphabet across four separate reference shapes, two tic-tac-toe grids and two X-shaped crossed lines, each shape appearing once in a plain form and once with a dot added to every cell.

• First tic-tac-toe grid (plain, no dots): nine cells, filled in reading order left-to-right and top-to-bottom with the letters A through I.
• Second tic-tac-toe grid (dotted — identical outline to the first, with a dot added inside each cell): nine cells holding J through R.
• First X-shaped grid (plain, no dots): four wedge-shaped cells around a crossing point, holding S, T, U and V.
• Second X-shaped grid (dotted — identical outline to the plain X grid, with a dot added to each wedge): four cells holding W, X, Y and Z.

How a Symbol Is Actually Built

A letter's symbol is drawn using only the grid lines that actually touch its cell in the reference grid — never the whole grid. A letter sitting in a corner cell of a tic-tac-toe grid keeps two connecting lines, forming an L-shaped bracket, which makes the four corner cells the sparsest symbols the system produces. A letter in a middle-edge cell (directly above, below, left or right of center) keeps three connecting lines, forming a broader U- or bracket-like shape open on one side. The exact center cell is the opposite extreme, not the blank space its position might suggest: it's the only cell bordered on all four sides at once, so its symbol comes out as a solid, four-sided box — and in the dotted version, that box just picks up a center dot instead of losing every line the way some descriptions wrongly assume. The X-shaped grids work on the same drawn-fragment logic using the four wedges formed where two crossing diagonal lines meet, rather than a nine-cell square.

A Worked Example: "WATCH"

W falls in the top wedge of the dotted X grid — a chevron pointing down from the top edge toward the crossing point, with a dot marking it as the dotted grid rather than the plain one. A is the top-left corner of the first plain tic-tac-toe grid, keeping only the lines on its right and bottom edges — a compact bracket whose corner sits at the bottom-right of the cell, open toward the top-left. T is the right wedge of the plain X grid, not a tic-tac-toe cell at all — a chevron pointing left from the right edge toward the crossing point, with no dot since this is the plain X grid. C is the top-right corner of the first tic-tac-toe grid, keeping the lines on its left and bottom edges — a bracket whose corner sits at the bottom-left of the cell, open toward the top-right. H is the bottom-middle cell of that same grid, keeping three lines along its left, right and top edges — a broad bracket open along the bottom edge, not the blank cell a mislabeled key might suggest. The one genuinely blank-looking exception in Grid 1, the fully-enclosed center cell, belongs to E, not H. Encoding a five-letter word this way makes clear just how much the symbol depends purely on cell or wedge position rather than on the letter itself; A and C, sitting in the mirrored top corners of the same grid, produce mirror-image two-line brackets for exactly that reason, even though the letters themselves have nothing in common.

Genuine Historical Masonic Use, and Its Real Limits

It's worth being precise about what "Masonic use" actually meant historically, since popular fiction tends to inflate it into something closer to a state-level intelligence cipher. Surviving 18th-century Masonic documents using this cipher were largely personal or lodge correspondence, gravestones, and ceremonial or membership records — a way of marking material as belonging to initiated members, more in the spirit of a private shorthand or a visual signature of belonging than a system built to withstand serious code-breaking. That distinction matters for understanding why it survived and spread the way it did: a cipher doesn't need real cryptographic strength to serve a social or symbolic function well, and pigpen has always done that job better than it's ever done the job of protecting a genuinely sensitive secret from a determined adversary.

Why It's Cryptographically Weak Despite Looking Complex

Underneath the unfamiliar symbols, pigpen is a simple monoalphabetic substitution cipher — each letter always maps to exactly the same symbol, every time, with no variation based on position or key. That's exactly the structural weakness frequency analysis exploits: in a message of reasonable length, the most common symbol is very likely standing in for E, the second most common for T, and so on, following the same well-documented English letter-frequency distribution this site's Caesar cipher reference discusses in more depth. The unfamiliar geometric shapes slow down a casual reader far more effectively than they slow down anyone actually applying frequency analysis with intent to break the message, which is the real, honest reason pigpen has never been used historically for anything requiring serious secrecy.

Two Real, Decoded Gravestones

The gravestone-marking use described above isn't a vague generalization — specific decoded examples survive and have been documented. The headstone of Thomas Brierley, who died in the 1850s and is buried in Mellor, Greater Manchester, carries a pigpen inscription at its foot that puzzled local historians and newspaper writers for much of the 20th century before being decoded as reading "Holiness of the Lord." On the other side of the Atlantic, one of the oldest stones in Trinity Church Cemetery in New York City, a burial ground that opened in 1697, carries a pigpen cipher of the same general type that decodes to the short phrase "Remember death" — a message meant to be visible to any passerby, but legible as actual words only to someone who already knew the cipher, which is a good, concrete illustration of exactly the kind of low-stakes, socially-scoped secrecy pigpen was genuinely built for.

Common Variants Worth Knowing

• The Rosicrucian cipher: a single 3x3 grid reused three times, with one, two or three dots added to distinguish which "pass" through the grid a given letter belongs to, rather than pigpen's separate plain-and-dotted grid pairs.
• The Knights Templar cipher: symbols arranged around a Maltese cross shape rather than tic-tac-toe and X grids, popularly (though not always reliably) associated with the medieval military order.
• Grid-order variants: some modern versions swap the standard grid-grid-X-X letter order for grid-X-grid-X, or interleave letters between the plain and dotted grids differently — a detail worth checking before assuming any two pigpen keys found online actually match.

Where Pigpen Shows Up Today

Modern-day use of pigpen is overwhelmingly recreational rather than genuinely concealing anything: escape rooms and puzzle-hunt props reach for it precisely because its symbols look cryptic and intriguing to a general audience without requiring a solver to already know real cryptanalysis; scouting and school cipher-and-codes units use it as a hands-on introduction to substitution ciphers; and it appears repeatedly in fiction and games with Masonic or occult themes, sometimes accurately researched and sometimes only loosely inspired by the real historical symbol set described above.