To narrow Android logs while developing a Kotlin app, use Android Studio Logcat’s key-value query syntax to filter by package, tag, message, or severity. For terminal output, use adb logcat tag-priority specifications instead; the two interfaces use different grammars.
Open Logcat and choose a filter
- Build and run your app on an Android emulator or physical device.
- In Android Studio, open View > Tool Windows > Logcat.
- Enter a query in the main query field. Logcat shows app and system messages as they arrive, and can display an exception with its stack trace.
Android Studio’s query field accepts structured terms such as package, process, tag, message, level, and age. Press Ctrl+Space in the field for query suggestions. You can also reuse saved query history or favorite filters.
Filter by app, tag, message, or event
Try these queries in Android Studio Logcat:
| Query | What it shows |
|---|---|
package:mine |
Logs from packages belonging to the open project. |
tag:MyTag level:DEBUG |
Entries for the specified tag at DEBUG or greater severity. |
message~:timeout |
Messages matching timeout as a regular expression. |
-tag:Noise |
Entries whose tag does not match the supplied text. |
(tag:foo | level:ERROR) & package:mine |
Project-package entries that match either the tag condition or the error-level condition. |
is:crash or is:stacktrace |
Crash-like entries or stack-trace entries. |
When you omit explicit operators, positive terms with the same key are combined with OR, while other terms are combined with AND. Parentheses and explicit | and & operators let you make the logic clear. Negation and regular-expression matching are documented for tag, package, message, and line. See Android Developers’ Logcat query documentation for the supported syntax.
Set a severity threshold in Android Studio
Use level: followed by a named level: VERBOSE, DEBUG, INFO, WARN, ERROR, or ASSERT. Levels are case-insensitive. The query is a minimum threshold, not an exact-match selector: level:INFO includes INFO and more severe entries, while level:WARN includes WARN, ERROR, and ASSERT.
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- Compatibility with certain third-party devices and accessibility accessories, including some hearing aids, may vary depending on manufacturer support, Bluetooth protocols, software compatibility, and regional firmware limitations. For additional hearing aid compatibility information, please refer to Samsung’s official support documentation.
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level:WARN— warnings and more severe entries.level:ERROR— errors and ASSERT entries.
As Android Developers explains, “The level query matches against the log level of the Logcat message, where the log entry level is greater or equal to the query level.”
Filter terminal output with adb
Unlike Android Studio’s named key-value queries, adb logcat uses whitespace-separated tag and minimum-priority pairs. The general command form is adb logcat [<option>] ... [<filter-spec>] ...; you can also run the device-side form, adb shell logcat ....
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To show the MyApp tag at DEBUG or higher and silence other tags, run:
adb logcat MyApp:D '*:S'The *:S specification makes the selected tag filters an allowlist. Quote it in shells where the asterisk would otherwise be expanded as a wildcard. To show warnings and more severe messages from all tags, use:
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adb logcat *:W| adb priority | Meaning |
|---|---|
V |
Verbose |
D |
Debug |
I |
Info |
W |
Warning |
E |
Error |
F |
Fatal |
S |
Silent |
For command options available on the connected device, check adb logcat --help. Android documents the command syntax and priorities in its Logcat command-line guide.
Write diagnostic logs in Kotlin
For app diagnostics, Kotlin code can use android.util.Log. Android’s debugging guide shows using the Log class to write messages and passing an exception as a throwable when you need its stack trace:
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- LIVE FAST. CHARGE FASTER: Focus more on the moment and less on your battery percentage with Galaxy A17 5G. Super Fast Charging powers up your battery so you can get back to life sooner.²
- MEMORIES MADE PICTURE PERFECT: Capture every angle in stunning clarity, from wide family photos to close-ups of friends, with the triple-lens camera on Galaxy A17 5G.
- NEED MORE STORAGE? WE HAVE YOU COVERED: With an improved 2TB of expandable storage, Galaxy A17 5G makes it easy to keep cherished photos, videos and important files readily accessible whenever you need them.³
- BUILT TO LAST: With an improved IP54 rating, Galaxy A17 5G is even more durable than before.⁴ It’s built to resist splashes and dust and comes with a stronger yet slimmer Gorilla Glass Victus front and Glass Fiber Reinforced Polymer back.
import android.util.Log
private const val TAG = "MyApp"
fun reportFailure(error: Throwable) {
Log.e(TAG, "Request failed", error)
}Use an appropriate log level for the message, then filter by the tag or severity in Logcat. Android’s debugging guide advises removing debug log messages and stack-trace print calls before publishing; a DEBUG flag with conditional logging is one way to keep development diagnostics out of release behavior.
If expected output is missing
Logcat output can be narrowed at more than one stage, so a display query may not be the only reason a message is absent. Android’s command-line documentation identifies compile-time settings that remove calls, system properties that set a minimum severity, application filtering, and display filters as possible filtering layers. Android log data is kept in circular buffers, including main (most application logs), system, and crash. If a message is not visible, review your query and applicable filtering layers, then consult adb logcat --help for options supported by the connected device.
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