guide · winscp

Compare a local file with the server copy in WinSCP

“Is what is actually on the server the same as what I have here?” WinSCP can hand a local file and a remote file to an external program, and Diffoniq shows them side by side. WinSCP’s own Compare Files extension only offers a fixed list of tools, so Diffoniq goes in as a custom command. Four fields, done once.

1. Add Diffoniq as a custom command

In WinSCP choose Commands → Custom Commands → Add and fill in the dialog like this:

Field	Value
Description	`Compare with Diffoniq`
Custom command	`"C:\Program Files\Diffoniq\Diffoniq.exe" "!^!" "!"`
Command type	Local command
Use remote files	leave unchecked

!^! stands for the local file and ! for the remote one. Leaving Use remote files unchecked is what makes this work: WinSCP then downloads the remote file into a temporary copy first and passes that, instead of a path your local programs cannot open.

The path above is the installer’s; if you use the portable ZIP, put in the folder you unpacked it to. Keep the quotes.

2. Compare

Select the local file in the left panel and the remote file in the right panel, then run Commands → Custom Commands → Compare with Diffoniq. Diffoniq opens with your local file on the left and the server’s copy on the right, differences marked line by line. Esc closes it and you are back in WinSCP.

Editing the server side writes back

Both sides are editable, because WinSCP hands over real files. If you change the right side and save, WinSCP uploads the modified copy to the server. It asks first — Overwrite remote file '…'? — but do not treat that as a safety net: it is WinSCP’s ordinary overwrite confirmation, it can be switched off in its preferences, and a reflex Yes is given quickly.

If you only ever want to look, add --read-only to the command line in step 1. Diffoniq then locks editing, saving and Synchronize for that call and shows [Read-only] in the title bar.

Good to know

Whole folders instead of one file at a time. If the server is also reachable as a Windows share, leave WinSCP out of it and give Diffoniq both paths yourself — "C:\site" and "\\server\share\site". That is a full folder comparison, and it works from a shortcut or a scheduled task as well. For a NAS this is usually the better route.
SFTP only, no share? Mount the server as a drive letter first (the help shows the rclone command) and compare the drive like any folder. Over a mount, stay on the Date/Size comparison; the help explains why.
What does not work: the FTP sites you can open in File Explorer. They look like folders but have no path behind them that a program could open.
.BAK stays on. When you save, Diffoniq keeps the original as a .BAK file, because here nothing else keeps a copy of what you had before.

The full reference, including the direct network comparison and the mount recipe, is in the help: File Managers and Transfer Tools.

Try it with your own server

Diffoniq runs on Windows 10 and 11, 64-bit. Every feature is available for 30 days before you decide.

Try Diffoniq free for 30 days See pricing

WinSCP is a product of WinSCP.net. Diffoniq is not affiliated with WinSCP.