--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -4770,16 +4770,17 @@ pref_InitInitialObjects()
       }
     }
   }
 
   rv = pref_LoadPrefsInDirList(NS_APP_PREFS_DEFAULTS_DIR_LIST);
   NS_ENSURE_SUCCESS(
     rv, Err("pref_LoadPrefsInDirList(NS_APP_PREFS_DEFAULTS_DIR_LIST) failed"));
 
+#ifdef MOZ_WIDGET_ANDROID
   // Set up the correct default for toolkit.telemetry.enabled. If this build
   // has MOZ_TELEMETRY_ON_BY_DEFAULT *or* we're on the beta channel, telemetry
   // is on by default, otherwise not. This is necessary so that beta users who
   // are testing final release builds don't flipflop defaults.
   if (Preferences::GetDefaultType(kTelemetryPref) ==
       nsIPrefBranch::PREF_INVALID) {
     bool prerelease = false;
 #ifdef MOZ_TELEMETRY_ON_BY_DEFAULT
@@ -4788,16 +4789,29 @@ pref_InitInitialObjects()
     nsAutoCString prefValue;
     Preferences::GetDefaultCString(kChannelPref, prefValue);
     if (prefValue.EqualsLiteral("beta")) {
       prerelease = true;
     }
 #endif
     PREF_SetBoolPref(kTelemetryPref, prerelease, true);
   }
+#else
+  // For platforms with Unified Telemetry (here meaning not-Android),
+  // toolkit.telemetry.enabled determines whether we send "extended" data.
+  // We only want extended data from pre-release channels due to size.
+  if (!strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "nightly") ||
+      !strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "aurora") ||
+      !strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "beta")) {
+    PREF_SetBoolPref(kTelemetryPref, true, true);
+  } else {
+    PREF_SetBoolPref(kTelemetryPref, false, true);
+  }
+  PREF_LockPref(kTelemetryPref, true);
+#endif // MOZ_WIDGET_ANDROID
 
   NS_CreateServicesFromCategory(NS_PREFSERVICE_APPDEFAULTS_TOPIC_ID,
                                 nullptr,
                                 NS_PREFSERVICE_APPDEFAULTS_TOPIC_ID);
 
   nsCOMPtr<nsIObserverService> observerService =
     mozilla::services::GetObserverService();
   NS_ENSURE_SUCCESS(rv, Err("GetObserverService() failed (2)"));