SpeedcubeQuest

What is two-sided PLL recognition?

Two-sided PLL recognition means naming which of the 21 PLL cases you are looking at from only the two sides you can see, without rotating.

You scan for four patterns, in this order, and take the first you find:

  1. 1. 3-bar

  2. 2. Lights

  3. 3. 2-bar

  4. 4. Bookends

Within that group, the first case that matches is your answer. Color rules are relative, never absolute: "opp" means opposite and "adj" means adjacent, both relative to the nearest pattern color. Learn the shapes, not the colors - every case turns up in four color combinations and may be mirrored.

Pattern system from the two-sided recognition guide by Mark Rivers.

Cases

35 cases
Tune how often each case comes up

Factors

Higher means that factor pulls more of the practice toward it. Set everything to zero for a plain even shuffle.

60%

Favour cases you've marked Don't Know or Learning over ones in muscle memory.

60%

Favour cases you get wrong more often.

40%

Favour cases that take you longer to recognise.

Resulting chances

Probability each case is the next one shown.

U
2.9%
J
2.9%
J
2.9%
F
2.9%
Z
2.9%
Z
2.9%
H
2.9%
U
2.9%
T
2.9%
R
2.9%
A
2.9%
Ga/c
2.9%
R
2.9%
Ga/c
2.9%
Gb/d
2.9%
A
2.9%
Y
2.9%
A
2.9%
V
2.9%
J
2.9%
N
2.9%
V
2.9%
R
2.9%
Gb/d
2.9%
T
2.9%
A
2.9%
Ga/c
2.9%
Gb/d
2.9%
Y
2.9%
F
2.9%
R
2.9%
Ga/c
2.9%
V
2.9%
Y
2.9%
E
2.9%

3-Bar

U - headlights Easy
J - 2-bar (orange) Easy
J - 2-bar (blue) Easy
F - 4 colors Easy

Double Lights

Z - 2-color 6-checker Easy
Z - adj edges & 4 colors Easy
H - opp edges Easy
U - 2:1 pattern & 3 colors Easy

Lights + 2-Bar

T - inside bar & 3 colors Easy
R - inside bar & 4 colors Easy
A - outer bar & 3 colors Medium
Ga/c - outer bar & 4 color Medium

Lone Lights

R - 5-checker Easy
Ga/c - 4-checker Hard
Gb/d - lights enclose opp Hard
A - lights enclose adj (but no checker) Medium

Double 2-Bar

Y - both outside Easy
A - both inside & bookends Easy
V - inside & no bookends Easy
J - same side & bookend Easy
N - same side & no bookend Easy

Outside 2-Bar

V - no bookend Medium
R - adj appears twice Medium
Gb/d - opp appears twice Hard
T - adj by bar & 4 colors Medium
A - opp by bar & 4 colors Medium

Inside 2-Bar

Ga/c - bookends adj color Hard
Gb/d - bookends opp col Hard
Y - no bookends Easy

Bookends No Bar

F - enclosed 4-checker Hard
R - adj appears twice Hard
Ga/c - opp appears twice Hard

No Bookends

V - inner 4-checker Hard
Y - outer 4-checker Medium
E - 5-checker w/ opp middle Hard

Statistics

Per-case recognition (average of last 10 attempts)

Answer some questions to see per-case stats.
Answer some questions to see which PLLs you mix up.

Frequently asked questions

Can every PLL case really be recognized from two sides?
Yes. Any two adjacent sides show six stickers, and that is always enough to pin down the case - the pattern hierarchy (3-bar, lights, 2-bar, bookends) plus the relative colors distinguishes all 21 PLLs at every angle. No cube rotation needed.
How do I get faster at PLL recognition?
Learn the patterns instead of memorizing color pictures - bars, lights and bookends stay the same across all four color combinations of a case. Then drill deliberately: the confusion matrix above shows exactly which case pairs you mix up, and raising their weight puts them in front of you more often.
Is this a PLL algorithm trainer?
No - this trainer is about naming the case fast, which is its own skill. For the algorithms themselves, ranked by how often top solvers actually use them, see the PLL algorithm database.
Do I need to know all 21 PLL algorithms first?
No. Recognition and algorithms can be learned side by side - use the case filters above to train only the cases you know so far. If you are still on 2-look PLL, recognizing corner permutation from two sides transfers directly once you go full PLL.