<p>Our understanding of the fracture behavior of oxide glasses is rudimentary at best, since the mechanical behavior is hidden behind complex disordered network structures. Here, we are locally decoding these complex networks, extracting scalar and tensor-based predictors, and quantifying how susceptible local regions are to experiencing mechanically induced rearrangements. Presenting the bond length fluctuation tensor, we find that shear transformation zones in network glasses highly correlate with regions of the highest variance in their bond stretch distributions projected into the direction of macroscopic deformation. Exclusively depending on the local geometry of the initial material state, our indicators are physically informative and can be evaluated directly from images with insignificant computational effort.</p>