This chapter delves into advanced techniques for measuring B cell mechanosensing and B cell receptor (BCR) conformational changes, which are pivotal in understanding the dynamics of B cell activation. We explore traction force microscopy (TFM), a method that tracks the displacement of fluorescent beads within elastic gels to quantify the forces exerted by cells, particularly immune cells, on planar surfaces. TFM has been instrumental in elucidating the role of substrate stiffness in immune cell adhesion and signaling, with applications in studying B cell activation thresholds and the forces involved in the formation of immunological synapses. Additionally, we discuss molecular tension sensor systems, which utilize force-resistant elements and reporter systems to monitor mechanical forces at the molecular level, providing insights into BCR activation and force-dependent signaling pathways. The chapter also presents site-specific labeling techniques for BCR and soluble immunoglobulin, employing ybbR and tetracysteine tags for precise fluorescent labeling, enabling the study of BCR conformational changes upon antigen binding. These methodologies collectively enhance our comprehension of the biophysical mechanisms underlying B cell activation and offer novel avenues for investigating immune cell mechanics in health and disease.