Othello / Reversi Rules

Every disc on an Othello board is two-sided, black on one face and white on the other, and a single legal move can flip a whole row of an opponent's discs to your own color at once — the entire game is a fight over board control that can swing dramatically from one move to the next, since a disc that was safely yours a turn ago can become your opponent's with one well-placed play.

Setup

The 8×8 board starts with four discs already placed in the center, two of each color, arranged diagonally opposite each other. Black moves first.

Making a Legal Move

A move is only legal if it traps at least one straight, unbroken line of the opponent's discs between the disc you're placing and another disc of your own color already on the board — in any direction: horizontal, vertical, or diagonal. Placing a disc that doesn't trap anything at all is not a legal move, full stop, even if there's an empty space you'd otherwise like to occupy. Every opponent disc trapped in that line flips immediately to your color.

The Forced Pass

If a player has no legal move available anywhere on the board, their turn is skipped automatically and play passes to the opponent — this isn't optional or a choice; a player with zero legal moves simply cannot play that turn no matter how much they might want to. If both players are simultaneously without a legal move, the game ends immediately even if the board isn't full.

Ending the Game and Scoring

The game ends when the board is completely full, or when neither player has any legal move remaining. Whoever has more discs of their own color showing on the board at that point wins — not whoever captured the most discs over the course of the game, only the final count on the board matters, since discs can flip back and forth multiple times before the game ends.

Why Corners Change Everything

A disc placed in one of the board's four corners can never be flipped by any legal move for the rest of the game, since no line can trap a corner disc from both sides simultaneously — this makes corners disproportionately valuable compared to every other square, and it's the single most important strategic concept in the entire game. A related, less obvious principle follows directly from it: playing a disc directly adjacent to an empty corner is often a mistake, since it can hand your opponent an easy, safe path to claim that permanently un-flippable corner square themselves.

A Contested, Layered History

This exact 8×8, flip-discs mechanic has two separate, well-documented origin threads that genuinely don't fully agree with each other. Reversi, the older name, was invented in England in 1883, with its exact originator disputed between two men, Lewis Waterman and John Mollett, who both separately claimed credit and neither ever conceded to the other. Decades later and apparently independently, Goro Hasegawa, then a Japanese high school student, developed his own version of the same core game around 1949, based on a similar game his father had taught him; he patented it in Japan in 1971 under the name Othello (a reference to Shakespeare's play, chosen for the black-and-white color reversal theme) and licensed it to a Japanese toy company in 1973, which mass-produced it into the version now sold worldwide. Hasegawa's own public account of how independently he arrived at the design shifted over time — earlier interviews described Othello as an improvement on existing Reversi, while later ones claimed a fully independent invention — which is why serious game historians treat the exact relationship between the two names as a genuinely disputed history rather than a single settled story.

The Arguments This Game Actually Produces

The most common dispute for new players is simply forgetting that a forced pass is mandatory rather than optional — a player realizing too late they had no legal move and wanting to "take it back" is a frequent source of friction, even though the rule itself isn't ambiguous. A second common argument is whether a disc trapped in more than one direction simultaneously by a single move flips in all of those directions at once (it does — every valid line from that move flips completely, not just one).

Questions People Still Ask Mid-Game

Can you choose to flip only some of the discs a move traps, leaving others unflipped? No — every disc in every valid trapped line from that move flips automatically; there's no selective flipping allowed.

What happens if the board fills up with one player far ahead but neither corner strategy played out as expected? The game simply ends at that point and whoever has more discs on the board wins — there's no additional scoring or tiebreak beyond the final disc count.

Is a diagonal line of trapped discs treated the same as a straight row or column? Yes — diagonal lines flip exactly the same way horizontal and vertical lines do, as long as the line is unbroken and ends in your own color's disc.