Which shape of carabiner is the strongest?

The strength of a carabiner is significantly influenced by its shape, and the D-shaped carabiner is recognized as being the strongest due to its design that aligns the load along the spine. When weight is applied to a D-shaped carabiner, it effectively distributes the load across its strongest section, which is the spine of the carabiner that faces away from the load. This alignment minimizes the risk of deformation even under heavy loads, making it the preferred choice for climbing, rescue, and other applications requiring high strength and reliability.

In contrast, other shapes like the oval and keylock may not support loads as efficiently as the D shape due to their design characteristics that can increase bending forces. While locking and keylock features enhance safety by preventing accidental gate openings or snagging on gear, their shape itself does not inherently contribute to the strength of the carabiner as much as the D shape does. Thus, the D-shaped carabiner is considered the strongest option available.