This data package supports the publication 'Complexity of crack front geometry enhances toughness of brittle solids' by Xinyue Wei, Chenzhuo Li, Cían McCarthy, and John M. Kolinski Nature physics (2024) - https://doi.org/10.1038/s41567-024-02435-x   DOI: 10.5281/zenodo.10604552     The data package includes  - data for material characterization in 'material_test.xlsx'; - segmented 3D crack data in "segmented_3D_crack_stacks" folder.     'material_test.xlsx' includes - shear modulus for Gel1, Gel2, Gel3, Gel4, and PDMS; - stretch v.s. engineering stress for the five materials.     'segmented_3D_crack_stacks' includes - 'sample_info.xlsx': metadata for all the cracks including the critically loaded cracks and the cracks with local    propagation in two sheets, with the following information: - 'crack_name' corresponds to the title of each tif file in the subfolders; - 'sample' indicates the material and thickness of the samples; - 'xy_scale_um' and 'z_scale_um' are the resolutions in microns in xyz direction ; - 's_start' and 's_end' provide the range of the valid slices, with s_end excluded. The first slice is s=0; - 'tile_s_start' and 'tile_s_end' provide the range of the valid slices of the tile scans. The tile scans            are taken for the measurement of strain energy release rate from the far field CTOD. Since the field of    view is large enough to cover the K-dominant region of Gel1, tile scan is not taken for Gel1; - 'remarks' are the comments for the data points (if applicable).   - 'critically_loaded_cracks': tif stacks for the binarized 3D cracks that are loaded to critical state.     Different materials and sample thicknesses are in separate folders.  - 'local_propagation': tif stacks for the binarized 3D cracks before critically loaded.