Abstract: Methods for manufacturing insulating glass units (IGUs) include providing an unsealed IGU assembly that has first and second sheets of glass material and at least one spacer frame between the first and second sheets and sealed to at least one of the first and second sheets. The unsealed IGU assembly defines an interpane space and an IGU passage providing fluid communication between the interpane space and an environment external to the interpane space. In some cases the method includes positioning a filling device next to the IGU passage and introducing a gas into the interpane space through the IGU passage using the filling device. In some cases the method includes delivering a sealing material or sealing structure to the IGU passage with the filling device to seal the interpane space. Corresponding systems for manufacturing IGUs are also provided.