The recluse spider spins high-aspect ratio silk ribbons unlike any other fiber, 6–8 μm wide and only 40–50 nm thin. In terms of stiffness and strength, these ribbons rival the highest-performing silks previously reported. Moreover, due to their extreme thinness, these ribbons can bend easily, facilitating surface conformation upon contact, thus introducing exceptionally strong adhesion. Using a unique spinning mechanism, the recluse spider uses organizes these ribbons into a linear metastructure of serial microloops. The loop junctions based on self-adhesion of the ribbon can sustain extremely high forces. The opening of such a sacrificial loop is non-destructive and releases hidden length, relaxing the fiber and restarting the stress–strain curve. This “strain cycling” substantially increases the toughness of the material, changing its tensile characteristics. We show that this stress–strain engineering via metastructure enables manifold toughness enhancements and demonstrated this in a synthetic, bio-inspired looped ribbon design.