This is a list of file synchronization software for which there are Wikipedia articles.
This is a comparison of the freeware (proprietary software release free of charge) file synchronization software.
This is a comparison of commercial software in the field of file synchronization.
These programs only provide full functionality with a payment.
As indicated, some are trialware and provide functionality during a trial period; some are freemium, meaning that they have freeware editions.