Swirl defects caused by oxide-related defects, namely oxide precipitates, have a detrimental effect on solar cell performance as these defects act as sinks for metal impurities. We suggest a method that allows the characterization of oxygen-related defects, which are suspected to be on the scale of a few tens of nanometers, which, despite their small size, have a macroscale effect on the minority carrier lifetime. The method consists of a suite of microscopy technique applied together to a) locate the defects and map them in a statistically relevant area, b) measure their density, size and distribution within the wafer bulk, and c) study their morphology and chemical state. As a result, we can understand the root-cause behind the formation of the oxide-related defects, their gettering ability, so we can apply processing techniques to mitigate them.