This dataset contains the experimental raw data from the mechanical testing of soft elastomers with different mixing ratios to produce different crosslinking degrees. The data have not been filtered. Every specimen is tested under tensile loading until full rupture. All samples had a thickness of 2mm. The initial length between grips was set to 30mm. The files are named according to: - the length of the pre-cut (c0mm/c1.2mm/c3.6mm/c6mm), - the (average) strain rate (0.001s-1/0.1s-1), - the mixing ratio (Xi0.5/Xi0.625/Xi0.75/Xi0.875/Xi1/Xi1.14/Xi1.33/Xi1.6/Xi2), - the number of the experiment up to the total number of repetitions under the same test conditions (R1/R2/R3). In addition, this dataset contains two videos showing the uniaxial deformation of: a) a highly crosslinked sample (Xi = 1) that produces sideways fracturing, b) a low-crosslinked sample (Xi = 0.5) that produces forward fracture. If this dataset is used for research or industrial purposes, please cite:M.A. Moreno-Mateos, P. Steinmann. "Crosslinking degree variations enable programming and controlling soft fracture via sideways cracking", npj Computational Materials 10, 282 (2024). https://doi.org/10.1038/s41524-024-01489-y.Further explanation regarding the specimen preparation and experimental setup can be found in the aforementioned work.