Why Won't My Rubik's Cube Solve? — Troubleshooting

Stuck with a cube that will not solve? Most of the time it is not the algorithm — it is a precondition one step earlier that was never met. Find the symptom below that matches yours, read why it happens, then follow the link to the stage that fixes it. If you cannot tell which case you have, type the 54 colours into the solver: it tells you first whether the state can be solved by turning at all.

Completely stuck: you cannot get past the first step

Symptom
You are learning for the first time and cannot tell which face to start from.
Why it happens
It is almost never the turning. Two basics are usually missing: each face's colour is decided by its centre piece — the centres never move — and turning a face is not the same thing as turning a layer.
How to confirm
Turn the cube a few times and watch the six centres. If their positions never change, the cube is in a normal state and all you need is the procedure.
Next step
Start with the fundamentals course: it explains the faces and the notation without a single algorithm. Then move on to the first Layer-by-Layer step, which needs no algorithm at all. Rubik's Cube Fundamentals Daisy step

The yellow cross will not appear

Symptom
You know the algorithm, but the top face keeps cycling between a dot, a line, an L and the cross.
Why it happens
What the algorithm produces depends on the shape you start from and on how you hold the cube: the dot becomes an L, the L becomes a line, the line becomes the cross. When shape and hold do not match, it looks as if the algorithm did nothing.
How to confirm
Hold the cube with the yellow face up and look only at the yellow edges: a horizontal line, an L (corner), or a single dot? Then check the orientation — the line goes horizontal, and the L goes with its corner at the front left, as the diagrams show.
Next step
Compare with the four cases, then run the algorithm to the end without rotating the cube or regripping. OLL Cross lesson

The second layer will not go in: the edge is stuck in the wrong slot

Symptom
A slot in the middle layer is empty, but the edge you need is neither on the top layer nor in its own slot — it is stuck somewhere else in the middle layer.
Why it happens
Once an edge sits in the wrong middle-layer slot it cannot be lifted out directly. You first swap it up to the top layer with the insertion algorithm, then place it properly.
How to confirm
Find that edge in the middle layer. If neither of its two colours matches the slot it currently occupies, this is the case.
Next step
Follow the "get the wrong edge out" part of the lesson: inserting once more with the same algorithm lifts it back to the top layer. Second Layer lesson

The yellow face will not finish: corner orientation

Symptom
The cross is done, but some yellow corners still do not face up — sometimes just one, and it refuses to come up.
Why it happens
Corner orientation needs one already-oriented corner to stay in place while you repeat the same algorithm. Starting again from a different position each time only cycles you through the same few cases.
How to confirm
Count how many top corners face up (0, 1, 2 or 4). For 1 or 2, hold the cube the way the lesson shows before you start.
Next step
The lesson handles each count separately. On the last step, turn the bottom layer — do not rotate the whole cube. OLL Corners lesson

One corner is wrong and no algorithm fixes it

Symptom
Everything else is solved, but a single corner's three colours do not match.
Why it happens
This state cannot be reached by legal turns. The cube keeps an invariant: the sum of all corner orientations is always a multiple of three, and twisting one corner breaks it. It normally comes from a cube that was taken apart, dropped, or had a corner turned by hand.
How to confirm
If the other seven corners and all twelve edges are correct and only this one corner is off, stop trying algorithms — turning on will scramble what is already solved.
Next step
This is a physical state problem, not a technique problem. This page gives no instruction for twisting pieces by hand; you can re-check your reading on the input page to rule out a misread sticker. Input Cube

One edge is wrong: its colours are swapped

Symptom
The same near-miss, but on an edge: one edge has its two colours the wrong way round.
Why it happens
The same kind of invariant — the number of flipped edges has a fixed parity, so a single flipped edge cannot come out of turning.
How to confirm
Confirm that every other edge is correct and only this one is flipped.
Next step
As in the previous case: a physical state problem. Check your reading on the input page first, so a misread sticker is not mistaken for a flipped edge. Input Cube

Only two pieces need to swap

Symptom
All the pieces are there, but two of them sit in each other's place — two corners, two edges, or one corner and one edge.
Why it happens
No turn swaps only two pieces; every algorithm moves more. Keep the distinction: two pairs swapping at once is a perfectly legal state (PLL solves it), while a single pair swapping is not, and usually comes from disassembly or from stickers being re-placed.
How to confirm
The colours all match, only the positions are exchanged, and no algorithm makes the state go away.
Next step
A physical state problem. Input the cube to get a definite answer instead of more attempts. Input Cube

The colours look wrong: stickers or input

Symptom
One face shows an impossible colour pattern, or the solver reports the state as invalid.
Why it happens
Three usual suspects: a sticker was peeled and glued back; the camera read one corner into two faces at once; colours were typed wrong — blue and green, or red and orange, are hard to tell apart in warm or dim light.
How to confirm
Look again in daylight on a white surface; confirm the centre colour of each face; then count the stickers — every colour must appear exactly nine times.
Next step
Type or re-check the colours on the input page. If a colour does not appear nine times, the problem is in the reading or the input, not in the cube. Input Cube