Saving COMSOL Files
The following options are selected from different menus and toolbars as described in The COMSOL Desktop Menus and Toolbars.
Saving a New Model or Application
To save a new model or application for the first time, or to update an already existing file, use one of the following methods:
Click the Save () button in the Quick Access Toolbar or Main Toolbar.
Select File>Save.
If you save an MPH-file that was previously saved in an earlier version of COMSOL Multiphysics, you will be asked to confirm the action. If you choose to continue, the file will be overwritten in an updated format that is only compatible with COMSOL Multiphysics version 6.1 or later. Select the Do not show this message again check box if desired. There is also a preference setting on the Save page in the Preferences dialog box. Clear the Warn before saving an application previously saved in an older version of COMSOL check box (selected by default) to turn off this question.
To save a model or application to a Model Manager database, use one of these ways:
Click the Save To () button in the Quick Access Toolbar or Main Toolbar.
Select File>Save To
See also The Save Window below.
Creating a Copy Using Save As
If the model has been saved before and you want to create a copy you can choose to save in one of the COMSOL file formats (see COMSOL MPH-Files, Model Files for Java, Model Files for MATLAB, and Model Files for VBA).
Select File>Save As. The Save As window opens, and from the Save as type list select COMSOL Application (*.mph) (the default), Model file for Java (*.java), Model file for MATLAB (*.m), or COMSOL File for VBA (*.vba).
In all cases, navigate to the location where you want to save the model, enter a File name, and then click Save.
Reverting to the Last Saved File
To open the last saved version of the file and reinitialize the UI, select File>Revert to Saved (). For Windows users, you can also customize the Quick Access Toolbar and then click the Revert to Saved button.
Compacting the History
The COMSOL files for Java and for MATLAB contain the entire history of the model, including settings that are no longer part of it. To compact the history so that the files only include the settings that are part of the current model, select File>Compact History. For Windows users, you can also customize the Quick Access Toolbar and then click the Compact History () button.
 
The compacted history can be wrong when the Interfering faces list in the Detect Interference node is active.
See also “History Logging Methods” in the COMSOL Multiphysics Programming Reference.
When Saving, Optimizing for Speed or File Size
You can choose to save COMSOL files (MPH-files) that are optimized for speed (the default, using uncompressed files that are faster to save) or optimized for file size (using compressed files). In the Preferences dialog box (see Preferences Settings), click Save and choose Speed or File size from the Optimize MPH-files for list.