The baseline ping


This ping is intended to provide metrics that are managed by the library itself, and not explicitly set by the application or included in the application's metrics.yaml file.

Note: As the baseline ping was specifically designed for mobile operating systems, it is not sent when using the Glean Python bindings.


The baseline ping is automatically submitted with a reason: background when the application is moved to the background. The baseline ping will be submitted at startup with a reason: dirty_startup, if the previous session was not cleanly closed. This only happens from the second start.

See also the ping schedules and timing overview.


The baseline ping includes the following fields:

Field nameTypeDescription
durationTimespanThe duration, in seconds, of the last foreground session. Only available if reason: background. 1
localeStringThe locale of the application. 2

See also the ping schedules and timing overview for how the duration metric relates to other sources of timing in the baseline ping.


The locale metric in the baseline ping is deprecated. Use client_info.locale instead.

The baseline ping also includes the common ping sections found in all pings.

Querying ping contents

A quick note about querying ping contents (i.e. for Each metric in the baseline ping is organized by its metric type, and uses a namespace of glean.baseline. For instance, in order to select duration you would use metrics.timespan['glean.baseline.duration']. If you were trying to select a String based metric such as os, then you would use metrics.string['glean.baseline.os']

Example baseline ping

  "ping_info": {
    "experiments": {
      "third_party_library": {
        "branch": "enabled"
    "seq": 0,
    "start_time": "2019-03-29T09:50-04:00",
    "end_time": "2019-03-29T09:53-04:00"
  "client_info": {
    "telemetry_sdk_build": "0.49.0",
    "first_run_date": "2019-03-29-04:00",
    "os": "Android",
    "android_sdk_version": "27",
    "os_version": "8.1.0",
    "device_manufacturer": "Google",
    "device_model": "Android SDK built for x86",
    "architecture": "x86",
    "app_build": "1",
    "app_display_version": "1.0",
    "client_id": "35dab852-74db-43f4-8aa0-88884211e545"
  "metrics": {
    "string": {
      "glean.baseline.locale": "en-US"
    "timespan": {
      "glean.baseline.duration": {
        "value": 52,
        "time_unit": "second"