Triangle faces are widest at the jawline and narrower at the forehead, so the goal is to add visual width and detail to the upper half of the face. Cat-eye, browline, and aviator frames work especially well, as their upswept lines and bold top edges draw the eye upward and balance the jaw. Avoid heavy, bottom-weighted frames, which can emphasize the width of the jawline.
Source: https://migafas.com/collections/triangle-face