Triangle face shape
Width builds toward the lower face.
How to recognize the outline
With the temples visible, compare your upper outline to the two jaw corners. A triangle or pear-shaped sketch is broader lower down. A beard or wide collar can add a separate outline, so follow the edge you can actually see.
Triangle or square?
On a triangle the sides widen toward the bottom. On a square the temple, cheek and jaw widths are closer. If the jaw edge is hidden, a styling trial can still be useful without settling on one label. See the square sketch.
What to check when trying glasses
Compare a defined top rim with a fine rounded pair of similar width. Watch whether the top edge draws attention upward or lets the jaw stay visually prominent. Check the bridge and temple pressure on both.
A haircut trial in the mirror
Compare the same part with a little volume at the temples, then with the sides smoothed down. Leave the ends alone during the trial so you can see what changed around the upper outline.
Compare your outline in the free face shape finder or ask friends to choose between two of your looks.