Today Synchi is finally public! It’s designed for syncing files between two locations (local or over SSH). It detects conflicts, and lets you decide what to do.
Why not rsync/Unison/Syncthing?
- rsync has no memory between runs and is one-way
- Unison needs to be installed on both sides
- Syncthing requires always-on daemons
Synchi runs on demand, works over SSH, and only transfers what actually changed.
I use it daily for syncing a shared folder between my machines and an android phone. Works great in combination with Tailscale/WireGuard so that you can sync files remotely.
Very nice! I’ll keep using unison for now as I need something stable and reliable, but I’ll keep an eye on the project and may switch to it eventually.
Totally fair, Unison is solid and I was inspired by it a lot, but its also the reason why I started working on my own version. I was frustrated with it because on Synology/SMB filesystems it kept seeing changed timestamps as modified files, so I’d constantly get fake changes and transfers. Synchi only treats a file as changed if the content hash actually differs.
Also, I once managed to delete my entire home folder because I tried syncing it with Unison to a server and it synced the empty remote folder back to my home, wiping everything. That’s exactly the kind of human error Synchi tries to prevent by being very explicit and verbose about what it’s about to do.
Thank you for keeping an eye on it!
It detects conflicts, and lets you decide what to do.
does it continue to sync the rest on conflict or does it halt for user input?
It compares everything first (scan, diff, hash), then halts before any changes are made. You see a full summary of what will happen, and approve each category separately (copies, deletes). It’s designed to be very transparent. Every change must be approved before anything is written.
Conflicts get their own interactive screen where you pick per-file: keep A, keep B, or skip. Nothing is written until you’ve resolved all of them.
If you want to skip the prompts, --yes flag auto-approves, but conflicts still halt for user input. Flags --force root_a or --force root_b are used for mirrors one way here conflicts are not possible.
but conflicts still halt for user input
i never understood this behavior. starting a large data transfer only to come back an hour later to find it halted at 5% due to some conflict. why not put those files at the end of the queue and resume with the rest?
It doesn’t work that way. Conflicts are resolved before any transfer starts. The flow is:
Scan both sides and compare (compute file hashes or just compare mtime, no data transferred)
Show conflicts if any → you resolve them
Show copy/delete summary → you approve
Only then does the actual transfer begin. So you never come back to find it halted mid-transfer. All decisions happen upfront while it’s just reading metadata, which is fast even for large trees.
This makes so much more sense than the Windows behavior.
