Syncthing on iOS: How to Make Möbius Sync and Synctrain Actually Work

ByPriya Nair

The Problem: iOS Won’t Let Apps Run in the Background

If you’ve tried Syncthing on iOS, you’ve hit the wall fast. The app syncs fine while it’s open — close it, and iOS suspends it, sometimes within minutes. There’s no workaround at the OS level. Apple’s background execution model prioritizes battery life and performance, not running a persistent sync daemon.

The Syncthing project has no official iOS client, and this is exactly why. What works as a quietly humming background process on Linux or macOS simply isn’t something iOS permits. Background tasks are scheduled by system heuristics — battery state, usage patterns, whether the screen is on — and apps can’t override that logic.

The Two Main iOS Clients

Möbius Sync

Möbius Sync, maintained by Pickup Infinity, is the longest-standing option. It embeds the Syncthing engine directly and exposes a familiar folder-based interface. The free tier caps syncing at 20MB; a one-time in-app purchase removes that limit and unlocks access to other apps’ sandboxes — essential for syncing an Obsidian vault or any other app that stores files privately.

It works well while the app is in the foreground. Background sync happens in brief windows, but iOS will eventually freeze the process. Many users find it stops syncing entirely after a day or so until they manually reopen it.

Synctrain

Synctrain, developed by Tommy van der Vorst (Pixelspark), is the newer alternative. It was designed with iOS constraints in mind from the start: tight integration with Apple’s background task APIs, native Siri Shortcuts support, and straightforward acknowledgment from the developer that background sync has limits. The developer ships a recommended Shortcuts pattern specifically for triggering a nudge-to-sync when the app has gone idle.

Synctrain also adds on-demand file streaming — access a file on a remote peer without downloading it first — and photo backup support. It’s actively maintained and well-regarded in the Syncthing community.

The Siri Shortcuts Workaround

The practical solution most users land on is a Siri Shortcut that forces the sync app into the foreground right before you need your files. It sidesteps background execution entirely. No background tricks needed.

For Obsidian, a basic shortcut looks like this:

  1. Open Möbius Sync (or Synctrain)
  2. Wait 15–30 seconds
  3. Open Obsidian

The wait time is the variable you tune. A small vault of plain markdown files syncs in well under 15 seconds on a local network. Larger vaults with PDF attachments or images may need more. Calibrate it once and leave it.

The trickier direction is syncing back from iPhone to Mac. Files you create or edit on your phone won’t reach your Mac on any predictable schedule — they sync whenever iOS decides to grant the app background time. If you write on both ends regularly, a second shortcut that briefly opens the sync app before closing Obsidian covers the return trip with roughly the same reliability.

Möbius Sync or Synctrain?

Already running Möbius Sync with the Shortcuts workaround? No urgent reason to switch. Möbius has a larger installed base, more community documentation, and years of forum posts to search when something breaks.

Synctrain is the cleaner starting point for a fresh setup. Native Shortcuts integration means the open-wait-launch pattern is formally supported rather than bolted on. It’s also the better fit if you want on-demand file streaming or automatic photo backup.

Either way, you’re working within iOS’s limits. No third-party app changes the underlying platform constraint.

A Note on Obsidian Vault Access

Obsidian on iOS stores vaults in a sandboxed directory. Both Möbius Sync and Synctrain can access it, but setup steps vary — and Apple occasionally changes how cross-app sandbox access works. Follow each app’s current documentation rather than a tutorial from a year ago; the steps may have changed.

Keep your vault lean if sync time matters. Plain text files are fast. Attached PDFs and images are the usual reason 15 seconds isn’t quite enough.

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