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. Recognize two exchanged groups
On a correctly reduced 4×4, exactly two complete edge groups can remain swapped while corners are correctly placed. This is PLL parity, a positioning exception. It differs from a flipped group and from three edges that simply need a normal cycle.
If you have not positioned the corners, finish that stage first. Mixed corner positions can make the edge problem difficult to diagnose.
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°.
Practice those widths in the notation lesson if necessary before trying the complete repair.
3. Apply the opposite-edge repair
2R2 U2 2R2 Uw2 2R2 Uw2 U2
This exchanges the UF and UB edge groups while restoring centers and preserving the corners.
- Two opposite groups swapped: rotate the whole cube sideways to put them at front and back on top, then apply the repair.
- Two adjacent groups swapped: apply the repair from any front with yellow up. Combining those exchanges leaves an ordinary three-edge cycle. Find its solved side, put it at 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 remains paired and the centers are solid. If three top groups remain out of place, solve that ordinary cycle; do not keep repeating parity.
Either OLL parity, PLL parity, both, or neither may occur in one 4×4 solve. You do not apply these algorithms automatically. The final lesson helps you choose the right branch 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 is 90° clockwise looking directly at that face. An apostrophe (′) reverses it; 2 means 180°. Keep the front fixed during an 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
Use one move at a time first. This prepared case teaches a specific action; use the lesson’s setup instructions to recognize when it applies to your own scramble.
Watch one worked example
UF and UB are exchanged in this prepared cube. Follow the single-inner-layer 2R2 moves and the two-layer Uw2 moves separately; 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. Arrow keys rotate the view when the cube is focused.
Copy this exact example on your own cube
Start with a solved 4×4, yellow up and blue front. Apply the setup below from left to right. This creates the example’s starting position. Keep this separate from the ongoing scramble you are solving through the course.
U2 Uw2 2R2 Uw2 2R2 U2 2R2Then follow the lesson sequence. If your cube’s color scheme differs, match the piece relationships using your own colors.
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
Inspect whether the two misplaced groups are opposite or adjacent. Use the repair, with the setup for your case, then reassess corners and edges before finishing.
Open a 4×4 Digital Cube for practiceOpens in a new tab so you can keep this lesson beside your practice. Check the lesson goal yourself; the Digital Cube does not grade it.
If you get stuck
I used the repair and now three edges are wrong.
If the original swap was adjacent, this is expected. Finish with the ordinary three-edge cycle, holding its solved side at back.
The centers are mixed after the sequence.
Check that 2R2 used only the second right layer and Uw2 used the top two layers. All seven moves must be completed.
Before moving on
Check your result
Your cube at this stage
The two-edge swap repaired
All groups and centers 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.
Check every item when you can do it yourself.