ArrowLoop

Two-way file synchronisation that shows you the plan before it moves anything.

Every other sync tool's main screen is a progress bar, which is a report on a decision somebody already made for you. Here you get the decision: every proposed change listed with its direction and the reason for it, each row unticked if you disagree, and nothing touched until you press the button.

What makes it different

It keeps a per-file record of what both sides looked like the last time they agreed. Without that third term, "the file is here but not there" is ambiguous: it means either "created over here" or "deleted over there", and those two call for opposite actions. Every two-way sync that loses data loses it there.

It refuses rather than guesses. A deletion goes to a trash instead of away. A run that would delete an implausible share of your files stops and says so. A side that lists nothing at all is never believed, because a disk that failed to mount looks exactly like a folder somebody emptied.

It reaches local folders, network shares, SFTP, S3-compatible storage, WebDAV clouds such as Nextcloud and OpenCloud, and the other services rclone speaks, with rclone compiled in as a library rather than shelled out to. There is no second executable to keep in step.

Where to go next

• Installing as a container, a desktop app, or a single binary.
• Configuring a job, every setting and what it is for.
• How it decides, the table the whole engine rests on.
• Safety, what stops it destroying anything.
• Command line for a machine nobody is looking at.
• When something goes wrong.

Without a password, anyone who reaches the interface can drive it

It asks for a password once one is set under Settings, Security, or through ARROWLOOP_PASSWORD_HASH. Until then keep it on your own network, or put it behind something that asks who the visitor is. It can start a job that deletes files.