Reversi (Othello) Strategy: Corners, Mobility, and Fewer Discs

Updated June 2026

Reversi takes a minute to learn and a long time to stop losing badly. The reason beginners struggle is that the obvious strategy — flip as many discs as you can — is almost exactly backwards. Strong play is about position, not count, until the very end. Here are the few ideas that turn the game around.

How it works, briefly

Players alternate placing discs of their colour. Each move must flank a line of the opponent's discs between the new disc and another of your own; every disc in that line flips to your colour. You must flip at least one disc or pass. When neither player can move, whoever has more discs wins. That flipping mechanic is volatile: a single move late in the game can swing dozens of discs, which is exactly why hoarding discs early is a trap.

Corners win games

The single most important fact in Reversi: a disc in a corner can never be flipped. Corners have no flanking squares beyond them, so once you own a corner it is permanent — and it becomes an anchor that lets you build stable, unflippable discs along both adjoining edges. Capturing corners, and denying them to your opponent, is the central strategic battle of every game. If you take nothing else away, take this.

The squares that give corners away

Because corners are so valuable, the squares next to them are poison. Watch two danger zones:

• X-squares — the diagonal neighbours of a corner. Playing one early hands your opponent the corner more often than not, because it opens the diagonal into it.
• C-squares — the edge cells directly beside a corner. They are less lethal than X-squares but still routinely let the opponent grab the corner.

Avoid both unless you have specifically read that the move is safe. A huge fraction of beginner losses are just an early X-square donating a corner.

Have fewer discs in the middle game

This is the counter-intuitive heart of Othello. In the opening and midgame, you generally want fewer discs than your opponent, not more. Why? Because the player with fewer discs usually has more moves available and more flexibility, while a bloated pile of your discs gives the opponent lots of lines to flip and squeezes your options. The discs you flip early are the ones most likely to be flipped right back. Count does not matter until the board fills up — only the final tally counts.

Mobility: keep your options, choke theirs

Flowing from the point above, the real currency of the midgame is mobility — the number of legal moves you have. Aim to keep your own move count high and drive your opponent's toward zero. A player with only one or two legal moves is forced to play whatever the board allows, which is often a C-square or X-square that gifts you a corner. Quiet, interior moves that limit how the opponent can flank you are usually stronger than splashy moves that flip a long line.

Build stable edges from corners

Once you hold a corner, extend along the edges from it. Edge discs anchored to a corner cannot be flipped, so they form a growing wall of permanent discs. Be careful, though: edge discs not connected to a corner can still be captured, and reaching for the middle of an empty edge can expose you. Grow edges outward from corners you already own rather than planting isolated discs along the rim.

Parity and the endgame

Late in the game, who plays last into a given empty region often gets to flip without being flipped back — this is parity. Try to arrange that empty pockets fall to you on the final move into them. As the board fills, the calculus flips entirely: now you do want to maximise discs, and the quiet positional play of the midgame pays off as your stable corner-and-edge discs convert into a winning count.

A practical mindset

1. Fight for corners; never volunteer the X-squares or C-squares that give them away.
2. In the midgame, prefer fewer discs and more moves — protect your mobility.
3. Force the opponent into low-mobility positions where they must hand you a corner.
4. Grow unflippable edges outward from corners you hold.
5. Switch to maximising discs only in the endgame, using parity to take the last move.

Play with these priorities and you will start winning games you used to lose by forty discs — often while holding fewer pieces right up until the final few moves.