The setup is common enough to be boring: a desktop where you actually play, and a Steam Deck for the sofa, the train, the bath. Same games, same account, one run you'd like to continue in both places.
The obstacle isn't the cloud. It's that the same save has two different addresses, and one of them is unguessable.
Why copying the folder across doesn't work
On the desktop, a Windows game writes to something like
%APPDATA%\SomeGame\Saves. On the Deck that same game runs through Proton,
which gives it a private Windows-shaped filesystem, and the save ends up at:
<library>/steamapps/compatdata/<appid>/pfx/drive_c/users/steamuser/AppData/Roaming/SomeGame/SavesThere's no rewriting one into the other by eye — the app ID in the middle isn't something you know, and it's different for every game. (The full anatomy of that path, and how it gets found without the number, is the previous post.)
So "just sync the folder" fails at the first step, before any of the usual sync-conflict problems even get a chance.
What actually happens
Checkpoint64 doesn't store a path. It stores the files, plus a record of which game they belong to and how they sat in the folder.
When you restore, the destination is worked out fresh on the machine doing the restoring. On Windows it resolves to the Windows path. On the Deck, the same save resolves into the right Proton prefix — found by looking, not by replaying whatever path the backup came from. The version you took on your desktop lands where the Deck's copy of the game will actually read it.
Nothing about your desktop's filesystem travels with the save. That's the whole mechanism, and it's why this works in both directions without configuration.
The part where we don't do what you might expect
Checkpoint64 does not silently sync your saves between machines.
There's no background process on the Deck noticing your desktop is ahead and quietly pulling it down. Restoring is a deliberate act: you open the save, look at the version list, pick one, and restore it.
That's a choice, not an omission. Silent two-way sync is precisely how people lose progress — the classic version is a launcher deciding your older copy is the newer one and overwriting three hours of play before you've noticed there was a conflict to resolve. We've written about that failure at more length. An automatic push in one direction is a backup; an automatic pull in the other is a gamble on the machine's clock being right.
What you get instead is every version kept and labelled, so choosing is cheap and being wrong is undoable. If you restore the wrong one, the one you meant is still sitting there.
The flow, in practice
Going from desk to Deck:
- Finish your session on the desktop. Auto-backup has already taken a version — it checks every 30 seconds and uploads when something changed.
- Pick up the Deck, open the save, hit Restore on the newest version.
- Play.
Coming back is the same three steps with the machines swapped.
The only rule worth remembering is the obvious one: don't play the same save in both places at once. Two machines both moving a world forward produces two divergent histories, and no tool can merge those for you — it can only let you pick one. If a save is genuinely being passed around rather than just carried between your own two machines, that's what the co-op lock is for; it makes "who has it right now" a thing the server enforces instead of a thing you remember.
What you need
Checkpoint64 is on Steam with a SteamOS + Linux build, so the Deck installs it like anything else in your library. The desktop side is Windows or Linux, free download or Steam, same account either way — the save doesn't care which one you used.
If you're juggling more than two machines, or a laptop that's been offline for a month, the broader version of this is syncing saves across PCs.
Download Checkpoint64 — it's free, and the free plan is real. No email list, no follow-ups.