Logcat

The Logcat tab is Android’s log, live, in the session page: what adb logcat would print, without adb on your machine. By default it shows only your app’s lines, so QA can see the error behind a broken screen and developers can follow their own tags without the rest of the system.

The session page reads it over ADB in the browser, from the device’s main, system and crash buffers.

When the tab appears

Logcat, Files and Terminal are the tabs that need ADB. They appear when the portal lets the session page open ADB (adb.browser, on by default) and you may use it: with adb.ownerOnly (the default) only the session’s owner and admins get them; everyone else sees the screen and DevTools only. See ADB tools.

Collecting starts once the device is first ready, whether or not the tab is open, and keeps going while the app restarts or another build is installed. The first lines are the last 2000 the device already had, so what happened during start-up is there too.

What you see

The toolbar

• This app / Everything: only your app’s lines, or the whole device. Your app is matched by its Linux user id, so all its processes count and a restart doesn’t lose it. If the id couldn’t be found, a line says The app’s user id is unknown, so every line is shown.
• The level menu: Verbose (everything, the default), Debug, Info, Warn or Error, each showing that level and above. Fatal lines always show.
• Filter tag or message: keeps lines whose tag or message contains the text, ignoring case.
• Pause / Resume: freezes the list at the last line; lines keep coming in underneath and show up on resume.
• Scroll to the newest (an arrow to a line): the list follows new lines while you are at the bottom and stops when you scroll up; this button takes you back and follows again.
• Clear (the eraser): empties the list.
• Download what is shown: a text file logcat-<package>-<date and time>.txt with exactly the lines that pass the filters, in the usual threadtime form (time, PID, TID, level, tag, message).

The lines

Each line has the time (MM-DD HH:MM:SS.mmm, in your browser’s time zone), the process id, the level letter, the tag (cut short; hover for the whole tag) and the message, wrapped. The letter and the tag are coloured by level:

Letter	Level	Colour
V	Verbose	grey
D	Debug	blue
I	Info	green
W	Warn	amber
E	Error	red
F	Fatal	dark red, bold

Lines from the crash buffer have a red tint behind them. While ADB connects the tab shows Connecting to ADB…; if that fails or the connection drops, Could not reach the device over ADB with the reason and a Reconnect button. Before the first line arrives the tab says Waiting for log lines…; when the filters hide everything, No line matches the filters.

The crash notice

When your app crashes (a FATAL EXCEPTION from AndroidRuntime, or a native crash’s *** *** *** from DEBUG in the crash buffer) and the report names the app’s process (Process: <package> for Java, >>> <package> <<< or the app’s uid for a native one), a notice The app crashed pops up on any tab with the first five lines of the stack trace. It stays for 15 seconds; its Logcat button opens this tab.

Common tasks

Catch the error behind a bug. Reproduce it, set the level to Error or Warn, and download what is shown to attach to the report.

Follow your own tags. Type the tag into the filter, or a word from your messages. Switch to Everything when the cause may be outside the app, such as ActivityManager killing it or the WebView’s own process.

Read a crash. Click Logcat in the crash notice and scroll to the red lines; switch the level to Error to see the stack trace alone.

Start from a clean log. Clear before reproducing, so the download holds only what happened since.

For a bug report with a screenshot, device and app details and this log (the whole device, whatever the filters), use Bundle in the Device card: see ADB tools.

In recordings

A recording keeps its own logcat, written on the server: the whole device, each line stamped with its time in the recording. Its player has a logcat panel with the same level and text filters, follows the playhead, and downloads the whole log as plain text or with colours. It doesn’t depend on this tab: a recording has its logcat even when nobody had the session page open.

Limits

• The tab keeps the last 20,000 lines in the browser; older ones drop out, also while paused. Reloading the session page starts over with the last 2000 lines the device has.
• Only the main, system and crash buffers; not events or radio.
• The log lives in the browser tab, not on the server. Two people watching the same session each collect their own.
• Logcat runs as a shell command: with redroid.shell: off on emulators, or adb.shell: off on phones, the tab stays empty. See Emulator provider.
• When the ADB connection drops, the tab stops getting lines. Reconnect opens it again, and logcat carries on from the last line it had.