Understanding the relationship between the structure of porous glasses and their failure behavior is crucial for developing reliable porous glasses for specific applications. In this study, we used nanometer resolution X-ray computed tomography (nano-CT) to image a controlled pore glass (CPG) with 400 nm-sized pores under in-situ uniaxial compression. Our results demonstrate that in-situ nano-CT is an excellent tool for identifying damage mechanisms in 400 nm pore glass. It allowed us to track changes in the shape of pores and pore walls during compression until the specimen failed. We also used computational tools to analyze the microstructural changes within the CPG sample, mapping displacements and strain fields. Additionally, we simulated the behavior of the CPG using a Fast Fourier Transform/Phase Field method. Both experimental and numerical data revealed local shear deformation occurring along bands, consistent with the appearance and propagation of ± 45-degree cracks.