Reversi
Outflank your opponent’s discs to turn them your colour — the classic strategy game of corners and edges, against the computer or a friend on the same screen.
At a glance
- Standard rules on the 8×8 board — Black moves first from the four centre discs — plus 6×6 and 10×10 boards.
- Play the computer on Easy, Medium or Hard, or a friend on the same device; possible moves are marked, and pointing at one shows which discs would turn.
- Hard searches ahead for about a second per move, values corners, edges and mobility, and plays the last 12 moves of an 8×8 game perfectly with an exact endgame search.
- The computer’s solver was checked on the 4×4 board, where perfect play is known: White wins 11–3.
- Small boards are solved: on 6×6, White wins 16–20 with perfect play. For 8×8, a 2023 computer study (a preprint by Hiroki Takizawa) reports that perfect play leads to a draw.
- Hints, undo, the full move list in standard notation (f5 d6 …), sound, full screen and keyboard play. Free, with no sign-up.
Step by step
How to play Reversi
- 1
Choose an opponent
Pick Computer and a difficulty, and Black (moves first) or White — or A friend.
- 2
Outflank
Place a disc so that one or more straight lines of your opponent’s discs lie between it and another of your discs — across, down or diagonally. Those discs turn to your colour.
- 3
Pass if you must
If you have no square that outflanks anything, your turn passes. If you can move, you must.
- 4
Count the discs
When neither player can move, the one with more discs on the board wins.
Features
Everything you need, nothing you don’t
Three levels
Easy to learn the rules, Medium for a fair game, Hard for a real fight — it knows the value of corners.
See every move
Dots mark the squares you can play; point at one to see exactly which discs it turns.
Passes handled for you
When a player has no move the turn passes automatically, and the game ends when neither side can move.
Learn from hints
Hint shows the computer’s choice; near the end it tells you the final margin with perfect play.
Two players, one screen
Play a friend with your own names and a running score for each board size.
Notation
Every game is recorded in standard notation, a1 at the top-left — paste it into any Reversi program to study.
Reversi strategy
- Corners can never be flipped. Take them when you can — and avoid the squares next to an empty corner (b2, g2, b7, g7 and the edge squares beside the corners), which tend to give it away.
- Fewer discs early is often better. Having many discs in the opening limits your own moves; keep your options (mobility) and squeeze your opponent’s.
- Edges are strong but not always safe. A lone edge disc can be outflanked along the edge.
- Parity in the endgame. Try to make the last move in each region of empty squares.
Reversi or Othello?
Reversi is the original name of the game, from the 1880s. The modern version — with the four centre discs placed in a fixed cross pattern and Black moving first — is sold under the trademark Othello, and those are the rules used here. JustTools is not connected with the Othello trademark owners.
FAQ
Frequently asked questions
Who moves first in Reversi?
What happens if I can’t move?
Is Reversi solved?
How strong is the Hard computer?
Can I play against a friend?
Is my game saved?
Keep going
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