When you run Liquid Data Diff Viewer, the 'Select Files to Compare' dialog is displayed.

This dialog is where you enter the two files you wish to compare. You can either type the full paths and file names, use the browse '...' button, or drag and drop files onto the dialog from Windows Explorer.

 

The 'Source File' is your original file with which you wish to compare a 'Changed File'.

The order of these files is important as you will get different comparison results if you swap the files round. This is especially important if you intend to save a 'diffgram' file as this will contain the changes required to apply to the 'Source File' to make it the same as the 'Changed File'.

When you click 'OK', the application will attempt to open the files using the correct Differencing Engine.