Cells have an extensive quality control network responsible for maintaining proteostasis. This network regulates protein synthesis, folding and transport. After decades of dedicated examination, the folding and stability characteristics of many individual proteins are well understood in vitro. However, understanding the kinetic process of protein folding in cells remains a grand challenge, whereby much of the proteome folds through discrete steps at different quality control checkpoints. We have recently developed a fluorogenic thiol-binding dye (TPE-MI) that can capture a snapshot of the balance of unfolded protein relative to folded states in intact live cells (Chen et al. 2017, Nat. Comm.). This approach does not require any expression of specific protein reporters, and has the potential to offer single-protein kinetic folding information for endogenous proteins at a proteome-wide scale. Here, we describe the application of this probe to determine proteome foldedness in cells following a variety of stressors. This knowledge will contribute to our understanding of disorders characterised by proteostasis imbalance, and will assist in targeting those proteins most prone to misfolding under stress conditions.