This article contains detailed description of synchronizing files. You may want to see simplified guide to the process instead.
WinSCP can synchronize content of local directory with remote one or vice versa or even mutually. Find the function in Commands > Synchronize. Synchronize dialog will appear, where you can select synchronization mode and configure options.
Once you confirm your options, WinSCP will collect list of differences in between the directories. If option Preview changes is enabled, you will be presented with the synchronization checklist, where you can select those synchronization actions you want to actually apply.
You can select files and directories for synchronization the same way you select them for file transfer.
Before using the function make sure that WinSCP knows correct timestamps of remote files, to avoid losing data.
There are three possible directions (targets) of synchronization.
With Local direction, changes from remote directory (source) are applied to local directory (target). Only the local directory is modified.
Remote mode is the same as Local, just in an opposite direction: changes from the local directory (source) are applied to the remote directory (target). Only the remote directory is modified.
In Both mode, both local and remote directories can be modified (both can act as both source and target).
There are three modes of synchronization.
With Synchronize files mode, files that are newer in a source directory than in a target directory are transferred to the target directory. Files in the source directory not present in the target directory are by default transferred as well (disable this using the option Existing files only). Files in the target directory not present in the source directory can optionally be deleted (enable option Delete files). In Both mode (see above), files not present in an opposite directory are considered new, hence they are transferred (unless Existing files only is enabled), but never deleted. In other words, in Both mode, no file is ever deleted.
With Mirror files mode, different (both newer and older) files in the source directory are transferred to the target directory. Otherwise the mode is the same as Synchronize files.
With Synchronize timestamps mode, timestamps of target files are updated to match timestamps of source files. It will not do any transfers, nor delete anything. Simply, whenever it finds the same file in both directories, it updates a timestamp of a target file to match the one of a source file. In Both mode, it always updates the older timestamp. The mode is available with SFTP protocol only.