1. Take turns
Players alternate placing X and O in any empty cell. In computer mode, board input locks while the computer chooses its reply.
Play 3D Tic Tac Toe Online — 3×3×3 vs Computer
Three aligned layers
Ready.Computer is thinking…
Top layer
Middle layer
Bottom layer
Explore all 49 winning lines
Choose a type, then step through lines to illuminate their cells.
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Game controls
Medium: takes wins, blocks immediate threats, then uses line potential.
You (X)
0Games ended without a winner
0Computer (O)
0Move history
- No moves yet
How to play 3D Tic Tac Toe
2. Read the layers
Each board uses columns A–C and rows 1–3. “Top B2” is the centre of the top board; the same coordinate on all three boards forms a vertical pillar.
3. Make a straight line
Win with three marks in one layer, through matching cells across layers, along a vertical-plane diagonal, or on a corner-to-corner space diagonal.
4. Follow the state
The amber dot marks the latest move. Hover or focus a cell to outline its matching row-and-column coordinate on every layer. The winning line remains labelled and highlighted.
The 49-line calculation
24 + 9 + 12 + 4 = 49. The three layers contribute 8 lines each (3 rows, 3 columns, 2 diagonals), for 24. Add 9 vertical pillars, 12 diagonals across the six vertical planes, and 4 corner-to-corner space diagonals.
The exact centre, Middle B2, lies on 13 lines: 3 straight axes, 6 face diagonals across the three planes through the centre, and 4 space diagonals. That is why it is both powerful and heavily contested.
Practical 3D strategy
- Control the centre. Middle B2 participates in 13 winning lines, so taking it creates options and denies them.
- Scan corresponding cells. After every move, check the same coordinate on the other two layers for a vertical threat.
- Watch space diagonals. A corner plus Middle B2 points directly to the opposite corner on the third layer.
- Create two-way threats. A fork leaves two different winning cells; a single reply cannot cover both.
- Block before building. Use Hint when learning—the explanation distinguishes wins, blocks, forks, and positional moves.
Interactive tactics
Load a position into the boards, find the move, or reveal the answer. Starting a new game exits puzzle mode.
1. Find the winning move
X has Top A1 and Top B1. Finish the same-layer row.
Top C1. It completes the top layer’s first row.
2. Block the space diagonal
O owns Top A1 and Middle B2. X must stop the opposite corner.
Bottom C3. It blocks the Top A1–Middle B2–Bottom C3 space diagonal.
3. Create a cross-layer fork
X owns Top A1 and Top C3. Find the cell that creates two opposite-corner threats.
Middle B2. It threatens Bottom C3 and Bottom A1 on two space diagonals.
Frequently asked questions
How do you play 3D Tic Tac Toe?
Players alternate placing X and O in empty cells across the top, middle, and bottom 3×3 layers. The first player to complete any straight three-cell line wins, including lines that cross layers.
How many winning lines are in 3×3×3 Tic Tac Toe?
There are 49 winning lines: 24 within layers, 9 vertical pillars, 12 diagonals across vertical planes, and 4 corner-to-corner space diagonals.
Is 3×3×3 Tic Tac Toe solved?
Yes. The 3×3×3 three-in-a-row game is a first-player win with perfect play, not a forced draw. A completely filled 27-cell board also cannot avoid a winning line.
Is this the same as Qubic?
No. This page uses a 3×3×3 board and three in a row. The Parker Brothers game Qubic is normally played on a 4×4×4 board with four in a row.
Can two people play on the same device?
Yes. Choose Local two-player mode for pass-and-play on one phone, tablet, or computer, then choose symbols and who starts.
How do the computer difficulty levels work?
Easy makes mostly random legal moves, Medium looks for immediate wins and blocks before using a positional heuristic, and Hard adds depth-limited alpha-beta search with a position cache.
Does the game work on mobile without downloading?
Yes. It runs directly in a modern mobile browser with no download. Moves are processed locally in the browser, and the page does not persist scores or settings.
Rules and implementation notes
- Variant: exactly three aligned marks on a 3×3×3 cube; the first completed line wins.
- Line generation: the game builds 24 same-layer lines, 9 pillars, 12 cross-layer face diagonals, and 4 space diagonals in code, then checks the resulting 49-line set after every move.
- Computer methods: Easy is mostly random; Medium uses immediate win/block tests and line weighting; Hard adds ordered, depth-limited minimax with alpha-beta pruning and a transposition cache. “Hard” is the strongest opponent on this page, not a claim of mathematically perfect play.
- Rules context: this 3×3×3 variant is a first-player win. It differs from Parker Brothers Qubic, the 4×4×4 four-in-a-row game studied by Oren Patashnik.
- Privacy: moves are processed locally. Scores and settings are session-only and are not stored by this page.
- Sources: NRICH’s 49-line counting problem, Cambridge University Press, Combinatorial Games: Tic-Tac-Toe Theory, and Patashnik’s 4×4×4 Qubic analysis.
- Last reviewed: 19 July 2026.