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!

Thanks! I’ve done some testing, nothing scientific, but I can tell you it transfers at about the same speed as other tools I tested, usually limited by network speed. I spent quite some time optimizing how small files are packaged together for transfer, so there’s no slowdown even with many small files compared to a single file of the same total size. Android APK idea is not bad though! I’ve published 2 Android apps before so will definitely look into it. Current Termux terminal approach is definitely not very user friendly.

Nothing wrong with that at all! You can set up a cron job to run Synchi every 5 minutes and it would work just fine. The only minor downside is some wasted compute since it rescans and hashes everything each run, even if nothing changed. For most files like text it’s negligible though.

In the future I might look into a lightweight daemon that uses Linux filesystem notifications (inotify) to trigger a sync when something changes.

Thanks! If you just need backup, with Synchi you set the ‘force=root_a’ in config, otherwise its bidirectional sync. If you need pure backups, rsync or similar might still be the better fit as they have some backup specific features.

I used Syncthing for years, it’s great (if you use it and you are happy, then you dont need to switch), but they are quite different. Syncthing requires daemons on all devices and can’t sync two local folders on the same machine. Synchi is on-demand, runs only on one side, and doesn’t care where the two root folders are.

I wrote a more detailed comparison here: https://jakobkreft.github.io/synchi/why.html

You are correct! no sub-file sync / binary diffing at the moment. It was my deliberate choice to keep complexity down. In practice, text files where diffing helps are tiny and transfer instantly anyway, and large files like images and videos almost never change partially. The main case where it would matter is something like large database files or VM images. That said, it’s not off the table for the future!

iOS is tricky since there’s no easy way to set up SSH access to the filesystem like you can on Android with Termux. So unfortunately not really supported at the moment. If you have a jailbroken device it might be possible, but that’s not something I’ve tested.

This is exactly how I use Synchi! Same idea but I use Logseq instead of Obsidian (very similar open-source alternative, worth checking out). Works great for syncing markdown notes between computers and my phone on demand. Of course I need to remember to sync before switching devices, but I prefer this then constant running in the background.

Haven’t thought about an Obsidian/Logseq plugin but honestly that sounds like a great idea… For now it’s CLI only, but I can definitely see the value.

I’m not too familiar with Steam Deck, but that sounds like it would work! As long as you can point Synchi at both save directories, it would keep them in sync and save you the manual copy-paste.

Great question! Let me sum it up here for others:

rsync is one-way only and has no memory between runs, every execution starts from scratch. Synchi is two-way, stateful (knows what changed since last sync), and content-aware (uses hashes, so no false positives from timestamp changes). It also handles conflicts explicitly instead of silently overwriting.

That said, rsync is still the better tool for backups and one-way mirroring. Synchi is for when you need true bidirectional sync.

Here is also a comparison with unison and syncthing: https://jakobkreft.github.io/synchi/why.html

Yes, you do need SSH set up on your phone. I’m using the same setup (Linux + Android). I wrote a short tutorial for it here: https://jakobkreft.github.io/synchi/termux.html

Also I use it with Tailscale so I can sync from anywhere not just local network.

Many sync tools like rsync are actually one-way (yes, only a mirror/backup). Two-way means changes on either side get synced to the other (Synchi helps you resolve conflicts). That said, Synchi can also do one-way mirroring if you set force=root_a in the config.

If you wish to sync between computer and Android, you don’t even need to install it on your phone. All you need is setup ssh connection and storage permission inside Termux terminal. I have written a short tutorial here: https://jakobkreft.github.io/synchi/termux.html if you wish still wish to run Synchi directly from Android, to sync between two android devices for example you can install it from source like this inside Termux terminal:

pkg install rust git

cargo install --git https://github.com/jakobkreft/synchi

Then add cargo bin to your PATH:

echo ‘export PATH=“$PATH:/data/data/com.termux/files/home/.cargo/bin”’ >> ~/.bashrc

source ~/.bashrc

After that you can just run synchi.

Yes! On android with Termux terminal.

(note: If you sync between computer and phone you don’t need to install it on your phone. One side only is enough.)

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.

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.

“Billions of people are getting robbed of their personal data, but what for?”

I love everything he has been doing recently. He is a master of story telling and goes surprisingly far into solving technology challenges, while keeping it fun and real. What an amazing transformation really

You can check out LabLog app on f-droid.

You save key value pairs, where you define keys yourself. And values can be text or photos.

I made the app, so if you have any questions I will be happy to help.

Yes, but most of these national apps I mentioned are already phone number based.

I also hate this. Phone numbers get recycled by operators, they are not owned by user, they just get assigned.

Not to mention sim swapping and privacy leakage by design.