This international clinical study will enroll participants with a suspected diagnosis of IPF/ILD. This study will characterize the disease behavior of IPF and ILD in the peri-diagnostic period. This objective will be achieved using a multidimensional approach assessing changes in pulmonary function, measured by daily handheld spirometry and site spirometry as well as assessing physical functional capacity at home (accelerometry) and at site (6-minute walk tests [6MWT]). Daily handheld spirometry or physical functional capacity assessments are not routinely performed in this participant population. By following participants' lung function before and after diagnosis using home spirometry, levels of physical activity, as well as self-assessment data from the participants (patient reported outcomes; PRO), the study would provide potentially more rapid information on disease behavior and eventually progression compared to usual clinic measurements that occur only every 3-6 months. By receiving data from daily handheld spirometry measurements, treating physicians may have an improved chance of detecting earlier and outside of hospital visits a decline in lung function that could potentially lead to improvements in both diagnosis and treatment for participants with IPF/ILD.