In Synchronize Dialog you select direction, mode and options for synchronization. To display the dialog go to WinSCP plugin menu.
Enter root directories for the synchronization into Local directory and Remote directory boxes. By default the current working directories will be used.
Use options Both, Remote or Local to select your preferred synchronization direction.
Use options Synchronize files, Mirror files or Synchronize timestamps to select your preferred synchronization mode.
The Delete files checkbox makes WinSCP delete files and subdirectories in target directory that are not present in a source directory. The option is not available for Both direction, because then such files and subdirectories are always considered as new and transferred into the opposite directory (unless Existing files only is checked).
The Existing files only checkbox makes WinSCP not to consider files and subdirectories not existing in an opposite directory as new. Such files and subdirectories will be ignored.
The Preview changes checkbox makes WinSCP request confirmation from you before each change it makes.
The Selected files only checkbox makes WinSCP synchronize only files and directories selected in any file panel. The option is not available, if no file or directory is selected.
The section defines criteria for determining whether two files (local and remote) are the same or not.
With Modification time checked (default) two files are considered different when they have different timestamps.
With File size checked two files are considered different when they have different sizes. The option is not available with Both direction selected. When using the option, you should avoid text transfer mode as it may change the file size.
When both options are checked, Modification time has higher priority. As a consequence, file is not considered updated, despite having different size, if the source file is older than the destination file.
When neither option is checked, existing files are considered the same always. So only new files are synchronized.
With Both direction selected, Modification time is always checked and File size unchecked.
For Synchronize timestamps mode checkbox Same size only is available. It makes WinSCP update timestamp of the files, that have same size in both directories, only.
Transfer settings box shows current transfer settings.
Use button Transfer preferences to configure transfer settings (alternatively you may double-click Transfer settings box).
You may want to change transfer settings particularly to exclude certain files and subdirectories from synchronization.
Check Use same options next time if you want to make your selected mode and options be default next time you use function Synchronize. This will not save transfer settings. You can change default transfer settings in preferences. Note that defaults affect function Keep remote directory up to date as well.