JavaScript Long Task Or Browser Freeze Detection Configuration

Feature

Germain UX RUM JS captures Javascript Long Task that occupies the UI main thread for 3 seconds or more. Usually that blocking and uninterrupted task causes:

• Bad animations and scrolling

• Browser Freeze

• Delayed time to interactive (TTI)

• High input and event handling latency

By default, this monitoring is enabled for each User Monitoring Profile.

What the Chrome team says about Javascript Long Task: https://web.dev/long-tasks-devtools/.

Configuration

Threshold

You can update long task threshold by setting settings.plugins.performance.longtaskThresholdMillis in the Init Script.

The following code sample shows how to collect long tasks only if equal or longer than five seconds.

const settings = germainApm.getDefaultSettings();
...
settings.plugins.performance.longtaskThresholdMillis = 5000; // in milliseconds
...
germainApm.start(settings);

KPIs

• KPI Name: “Javascript Long Task - Browser Freeze”. More details.

Example

Component: RUM JS

Feature Availability: 2022.2 or later

Browser Support: only latest Chrome, Edge and Opera