Preview a SyncToy Run

Pressing the Preview button allows you to see the actions that SyncToy will take when it runs a folder pair. You have the opportunity to review the list of operations and ensure that SyncToy will do what you expect.

Select the folder pair you want to preview.
Click on the Preview button to preview the folder pair.

The preview display looks like this:

Some of the features of the preview display are:

Operations that overwrite or delete files are shown in red.
You can exclude any operation from the SyncToy run by unchecking it in the preview display. Note that Create Folder operations cannot be excluded from the SyncToy run because other operations would then fail.
You may double-click on any row to open the file listed. For example, if you double-click on an image file, you will view the image. Similarly, if you double click on a text file, you will see the contents of the text file.
A context menu appears if you press the right mouse button while the mouse pointer is over the main preview list. This menu gives you another way to open the file underneath the mouse pointer, or to select or unselect all of the rows in the list. You can also launch Windows Explorer from this menu.
Note that you cannot open executable files in this display because that would potentially be dangerous.
You can sort the preview list by clicking on any of the column headers. Click the header again to sort the column in descending order. Sorting the preview display does not change the order in which the operations will be performed. It simply allows you to view the operations differently.
You can resize any of the preview list columns by clicking on the vertical line in the header at the right edge of the column, and dragging it to the right to expand the column, or to the left to condense it.
At any time you can position the list highlight on the first occurrence of any of the operation types by choosing the appropriate operation type in the "Go To" drop down list at the top of the screen. This can be handy if there are many operations displayed and you want to review a particular operation type. Choosing an operation type from the drop down list automatically sorts the main preview list by operation and positions the row highlight on the first operation of the type you selected.
SyncToy reports the files and the number of bytes that it can avoid copying because the files are already in sync. One of the primary benefits of using SyncToy is that it can often save time by avoiding unnecessary copying.
When you have completed reviewing the preview display, you can start a SyncToy run to perform the displayed operations by selecting Run at the bottom of the screen.
By unchecking items in the Preview screen, the unselected items will only be unselected for the run being previewed. They will not remain unselected for subsequent runs.