A cross-device save writes progress to a platform’s cloud storage (keyed to the logged-in player) instead of the browser’s local storage, so the same save loads on any device. The game calls a load before gameplay starts and a save on meaningful state changes, treating missing data as defaults rather than an error.
At a glance
| Fact | Value | Source |
|---|---|---|
| Cloud saves require player to be authorized | on platform | |
| Local storage vs platform storage | device-only vs cross-device | wiki.playgama.com |
| Missing save keys should return | null, use defaults | wiki.playgama.com |
A cross-device save is really two decisions: where the data lives, and when your game reads and writes it. Instead of writing progress to the browser’s own local storage (which is tied to one device and one browser), the game writes to a storage location the platform keeps on its servers, keyed to the player’s logged-in account. Load that data once before gameplay starts; save it again only on meaningful changes – level complete, purchase, settings change – not every frame.
The Playgama Bridge Storage module handles this automatically: it picks the most suitable storage for the current platform, including cloud saves when available, so the game code doesn’t need per-platform branching. Load with bridge.storage.get([...]) and save with bridge.storage.set(...); never write player data straight to localStorage or the engine’s own local persistence (PlayerPrefs, local files), or it won’t reach the cloud.
What happens when there’s no saved data yet?
- Missing keys return null, so keep defaults rather than treating it as an error.
- Unity WebGL builds reach browser storage APIs through a
.jslibplugin (JavaScript interop); Godot 4 uses the JavaScriptBridge singleton for the same purpose. - Bridge plugins exist for plain JS, Unity, Construct 3, GDevelop, Godot, GameMaker, Defold, Cocos Creator and Scratch, so the same save/load calls work regardless of engine.
Two storage types worth knowing: local_storage (device-only, no cross-device sync) and platform_internal (platform cloud, cross-device, requires an authorized player). bridge.storage.defaultType tells you which one the current platform prefers – use that by default.
Sources
- Playgama Bridge – getting started
- Playgama Bridge – Storage API
- Unity manual: interacting with browser scripting
- Godot docs: exporting for the Web
- MDN: Web Storage API
Related questions
Does cross-device save require the player to log in?
Yes – cloud/platform storage is tied to an authorized player account. Without authorization, saves stay in device-only local storage.
How often should a game write to cloud storage?
On meaningful state changes only – level complete, purchase, settings change – not every frame, to avoid unnecessary write calls and race conditions.
What should happen if no save data exists yet?
Treat missing keys as null and load your default state; this is a normal first-run case, not an error condition.
Last updated: 24 September 2026