Science has been one of the foundations of the success of the Montreal Protocol. This assessment highlights advances and updates in the scientific understanding of ozone depletion since the 2018 Scientific Assessment of Ozone Depletion and provides policy-relevant scientific information on current challenges and future policy choices. The latest edition of the quadrennial assessment report of the UN-backed Scientific Assessment Panel to the Montreal Protocol on Ozone Depleting Substances confirms the phase out of nearly 99% of banned ozone-depleting substances.