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Monitoring Browser Long Tasks

Experience collects information about long tasks that happen during page loads. According to the RAIL Model, tasks that are running for longer than 50ms and blocking the main thread are considered long and are recorded by Sematext Cloud.

Long tasks can cause issues such as:

  • Clunky animations and scrolling affecting user experience
  • High input latency
  • Long delay in events handling
  • Delayed time when your application becomes interactive

Thus, it is critical to monitor long tasks executed as part of your application's handling of user requests.

Page-Load Overview

The aggregated data about long tasks are visible on the page loads overview of your Experience App. You can check the number of long tasks and their average duration:

Page Loads Overview

Page-Load Details

In addition to the charts showing long tasks on the page-loads overview, each individual page-load details screen also contains information about long tasks detected during both hard and soft page loads. Each long task is described by its timestamp, and duration.

Page Load Details

Browser Support

The following browsers support the Long Tasks API allowing Sematext Experience to gather the data about long tasks:

  • Google Chrome starting from version 58,
  • Microsoft Edge starting from version 79,
  • Opera,
  • Samsung Internet starting from version 7.0.