Glass range: yes, they are freezer friendly. Reusable plastic range: yes, they are freezer friendly. Before placing in the freezer, we recommend the containers are not overfilled. We also advise the edges connecting the tray and lid are free from food and moisture, give these a wipe down first. It is important that cooked food is completely cooled down and any condensation which has formed in the lid is wiped off before placing in the freezer. Otherwise, the condensation can form into ice in between the edges.