Open source. Peer-to-peer. Your data never touches a third-party cloud.
Syncthing is free, open source, and syncs files directly between your devices over your local network (or the internet, encrypted, when you're away from home). No company stores a copy. The tradeoff is more setup than iCloud or Dropbox, and Syncthing on iOS is currently a third-party paid app.
Pick this if you care about keeping your notes on your own devices, you're comfortable installing software from open-source projects, and you have at least one Android device or are willing to pay for an iOS Syncthing client.
Run it. Syncthing opens a web admin page in your browser at http://127.0.0.1:8384.
The admin page shows your device's unique ID (a long string starting with letters). You'll need this to pair with your phone.
Step 2: Create a Keepance folder and share it
Decide where your Keepance workspace will live on your computer. A clean choice is ~/Keepance-Sync/.
In the Syncthing admin page, click Add Folder.
Folder Label: Keepance. Folder ID: leave the auto-generated value. Folder Path: the path you picked above.
Save. Syncthing now watches that folder for changes.
Step 3: Point Keepance at the synced folder
In Keepance, open File → Open Workspace.
Pick the folder you set up in Syncthing (for example, ~/Keepance-Sync/).
Click Open.
[Screenshot: Syncthing admin page with the Keepance folder configured]
TODO: real screenshot of the Syncthing admin page showing a configured Keepance folder.
Step 4: Install Syncthing on your phone
Android (recommended)
Install Syncthing-Fork from the Play Store. (The original Syncthing-Android was deprecated; Syncthing-Fork is the maintained successor.)
Open the app. Tap the menu, choose Devices, then + to add a device.
Use the device ID from your computer's Syncthing admin page. Your phone will appear on the computer side asking to be approved; approve it.
Then on the phone, tap Folders, accept the incoming Keepance folder share, and pick a destination on your phone (for example, /storage/emulated/0/Keepance/).
iOS
iOS does not have an official Syncthing client. The community-recommended option is Möbius Sync from the App Store. It's a paid app (one-time purchase), and it follows the same pairing flow: add your computer's device ID, accept the Keepance folder share, and pick where to store it on the phone.
If you don't want to pay for an iOS Syncthing client, the iCloud Drive workaround is the better fit on iPhone.
[Screenshot: Syncthing-Fork on Android with the Keepance folder paired]
TODO: real screenshot of Syncthing-Fork on Android showing the paired Keepance folder.
Step 5: Read your files on your phone
Once the folder finishes syncing, browse to your Keepance folder using your phone's file manager. On Android, the built-in Files app or Google Files works fine. Tap any .md file to read it (Android renders Markdown as plain text by default; install a free Markdown reader like Markor for nicer rendering).
Limitations to know
Treat your phone as read-only for now. Syncthing handles conflicts by creating a file with .sync-conflict in the name. The cleanest workflow is to edit on one device at a time.
Both devices must be running. Syncthing is peer-to-peer, so files only sync when both your computer and your phone have Syncthing actively running. Sleep your laptop and the sync pauses until it wakes up.
iOS Syncthing costs money. Möbius Sync is a one-time purchase. There is no free official iOS client.
First sync can be slow over cellular. If you're not on the same Wi-Fi network as your computer when you first pair, the initial sync goes over Syncthing's relay servers and can be noticeably slower than local sync.
What's next
For a less-technical option that works on both iOS and Android with no extra software cost, see the Dropbox guide. For Apple-only users, the iCloud Drive guide is the simplest path.