The FRIB diagnostics system covers an extensive range of primary and secondary beam intensities of 14 orders of magnitude and requires continuous improvements. The linac diagnostic system has provided straightforward linac commissioning and supports the development of many primary heavy ion beam species for producing rare isotopes. The diagnostics system for the secondary beam has a unique feature of detecting and measuring low-intensity rare isotope beams. This talk will report on the performance of the FRIB diagnostics system and ongoing improvements.