Screenly is a cloud service, but the playing happens on the device. That one fact explains most of the timing you will observe.
Two independent states
Online means the device is checking in with us. In sync means it has downloaded everything assigned to it.
They fail separately, so a screen can be:
| Online | In sync | What that means |
|---|---|---|
| Yes | Yes | Healthy and current |
| Yes | No | Downloading. Still showing the previous content meanwhile |
| No | Yes | Offline, but playing exactly the right thing |
| No | No | Offline, will catch up when it reconnects |
The third row is the one people find surprising, and it is the point of the design.
What survives an outage
Files you uploaded play from the device’s own storage, and schedules are held on the device too. A screen carries on showing the right content at the right time with no internet at all.
What stops is anything that needs the network. A web page or an app pulling live data is skipped while it cannot reach its source, and rejoins the rotation when the connection returns.
Why changes are not instant
A change reaches a screen on its next check-in, then the screen downloads whatever it does not already have and switches once the download is complete. There is no gap in playback: it keeps showing the old content until the new content is fully there.
In practice that means a minute or two on a healthy connection for the instruction, plus download time. Video takes considerably longer than images. Allow around fifteen minutes before deciding a change did not work.
The trap in this
An offline screen keeps playing, so nobody notices. A dark or stale screen can go a week without anyone mentioning it, which is why offline alerts matter more here than they would in a system that failed loudly.
Deeper: Status and sync, Storage and caching.