What are you trying to fix?
Three problems people arrive here with. Each page includes an honest read on the free options too — if one of those fits you better, use it.
Replace SMB
Replace Windows file sharing
Windows file sharing breaks after every update. Replace it with a LAN transfer app that does not use SMB, so share names, network discovery and 0x-errors stop being your problem.
For offices
Office file sharing on a local network
Move files between office computers over your own network at 60–115 MB/s on wired gigabit. No cloud round trip, no shared folders to configure, no per-seat cloud storage bill.
Shared files
Stop people overwriting each other's work
Windows tells you a file is locked by "another user" without saying who. Oxolan names the person holding it, and refuses the second opener before they waste an edit.
No cloud
File sharing without the cloud
Share files between computers without uploading anything. Transfers run directly across your own network, so client work never sits on a third-party server.