A reduced cube with last-layer orientation complete and corners positioned.
Yellow up. The repair exchanges top-front (UF) and top-back (UB) groups.
1. Recognise two swapped edge groups
On a correctly reduced 4×4, exactly two complete edge groups can still be swapped even when the corners are in the right positions. This is PLL parity, which affects where pieces are positioned. It differs from a flipped group or three edges that just need a standard cycle.
If the corners aren’t in their correct positions, finish that stage first. Misplaced corners can make it harder to diagnose the edge problem.
2. Read the inner-layer move carefully
2R2 means turn only the second layer from the right by 180°. It does not mean R2 or Rw2. Uw2 turns the top two layers together by 180°.
If needed, use the notation lesson to practise turning the correct layers before trying the full repair.
3. Apply the opposite-edge repair
2R2 U2 2R2 Uw2 2R2 Uw2 U2
This exchanges the UF and UB edge groups while restoring centres and preserving the corners.
- Two opposite groups swapped: rotate the whole cube sideways so one group is at the front of the top layer and the other is at the back, then apply the repair.
- Two adjacent groups swapped: apply the repair with yellow up, whichever side is at the front. Together, the two swaps leave a standard three-edge cycle. Find the solved side, hold it at the back and use the final-edge cycle once or twice.
Complete all seven moves before checking the result.
4. Finish and inspect
Check that every edge is still paired and the centres are solid. If three edge groups on top are still out of place, finish with the standard three-edge cycle instead of repeating the parity algorithm.
A 4×4 solve can have OLL parity, PLL parity, both or neither. Use a parity algorithm only when its case occurs. The final lesson helps you decide what to do when solving from a fresh scramble.
Need a reminder of the move notation?
R right · L left · U top · D bottom · F front · B back. A plain letter means a 90° clockwise turn as you look directly at that face. An apostrophe (′) reverses the turn. A 2 means a 180° turn. Keep the same face towards you throughout the algorithm.
Rw turns the rightmost two layers together. 2R turns only the second layer from the right. 3Rw turns three layers. x rotates the whole cube like R, so the old front becomes the new top.
Watch, then try
Work through an example
Start by stepping through the example one move at a time. This example demonstrates a specific action. Use the lesson’s setup instructions to recognise when that action applies to your own scramble.
Watch one worked example
In this prepared cube, the edge groups at UF and UB are swapped. For each 2R2 move, turn only the single inner layer. For each Uw2 move, turn both top layers together. Both widths are essential.
Example grip: yellow up · blue front · red right at the start. Follow any written whole-cube rotations.
0 / 7
Loading 3D cube…
Prepared position · 0 / 7 moves
Use Next move to follow the sequence.
Drag to inspect other faces. When the cube has focus, use the arrow keys to rotate the view.
Copy this exact example on your own cube
Start with a solved 4×4, with yellow on top and blue at the front. Apply the setup moves below from left to right. This gives you the starting position for the example. Keep this separate from the scramble you’re solving throughout the course.
U2 Uw2 2R2 Uw2 2R2 U2 2R2Then follow the lesson sequence. If your cube has a different colour scheme, use your own colours to identify the corresponding pieces.
Compare the starting position and the result
Drag each cube to inspect its other faces.
Explain it to yourself
Check your understanding
Now use your own cube
Your turn
Check whether the two misplaced groups are opposite or adjacent. Set up the cube for your case and apply the repair, then check the corners and edges again before finishing.
Open a 4×4 Digital Cube for practiceThe Digital Cube opens in a new tab so you can keep this lesson open while you practise. Check for yourself whether you’ve met the lesson goal, as the Digital Cube doesn’t assess your result.
If you get stuck
I used the repair and now three edges are out of place.
If the original swap involved adjacent edge groups, this is expected. Finish with the standard three-edge cycle, holding the solved side at the back.
The centres are mixed after the sequence.
Check that 2R2 turned only the second layer from the right and Uw2 turned the top two layers. Complete all seven moves.
Before moving on
Check your result
Your cube at this stage
Two-edge swap fixed
All groups and centres are intact. An ordinary three-edge cycle may remain, as shown here; finish it with the 3×3 method.
Confirm these on your cube. Watching the animation alone does not complete the lesson.
Tick each item when you can do it yourself.