Live logs
The device writes a lot. Live logs is the stream, plus the filters that make it readable.
Starting
Section titled “Starting”- Select the device.
- Open Live logs.
- Optionally scope to an app, then drive the app on the device.
Output appears as it is written. There is nothing to enable on the phone and nothing to add to your build.
Filtering
Section titled “Filtering”Three filters, and you generally want more than one:
- By app. Restricts to one process. Start here.
- By keyword. Substring match across the line. Your own log prefix is the most useful thing you will ever type in this box.
- By process. Broader than by app — useful for chasing a system daemon that is complaining about your app rather than the app itself.
What you will see besides your own lines
Section titled “What you will see besides your own lines”The system logs heavily, and a lot of it is noise you learn to ignore. Some of it is not:
| Line | Worth reading |
|---|---|
| Memory pressure warnings | Yes — often the last thing before a jetsam kill |
| Watchdog / hang reports | Yes — the main thread was blocked long enough to be noticed |
| Network reachability changes | Yes, when chasing a request that failed intermittently |
| Layout constraint conflicts | Yes, and they are usually your fault |
| Routine daemon chatter | No |
Saving
Section titled “Saving”Save writes the current view to a text file — filter included, so a saved log is the filtered log, not the raw firehose. That is usually what you want to attach to a ticket, but it is worth stating in the ticket which filter produced it.
For a failure you can reproduce, the useful capture is: clear, reproduce, stop, save. A file starting ten minutes before the event is much harder for the next person to read.
When logs run out
Section titled “When logs run out”Live logs show what the app chose to say. When the app said nothing — it froze, or it vanished — the log ends without explaining itself. Two follow-ups:
- A sudden end with no exception usually means the process was killed. Check memory in a performance capture; a jetsam kill after a memory climb looks exactly like this.
- A crash writes a report even when it logs nothing. See Crash logs.