Device definitions

You can customize the details of the devices used to test your site. For example, you can set up a device that closely resembles a typical customer.

List of emulated devices

Default devices

Four devices are configured by default.

The Mobile and Desktop devices match the settings used by Lighthouse and PageSpeed Insights. Note that there may still be difference in performance metrics in different environments.

Name Bandwidth Round-trip time CPU throttling
Mobile 1.6 Mbps 150ms 4x
Mobile Fast 12 Mbps 70ms 2x
Desktop 8 Mbps 40ms 1x
Desktop Fast 100 Mbps 2ms 1x

If you signed up for your account before September 2019 these defaults may differ.

Configuring devices

To modify the default devices, or create new ones, click on the gear icon next to the device dropdown when configure a new page.

Enter device settings

This will show the list of existing devices in your project.

Details on each device

Click on the pencil icon to edit an existing device, or click Add new device to create a new custom device configuration.

Edit device


This setting limits how much data can be transferred per second.

Round-trip latency

When running a test each network packet will be held back for this amount of time.

Form factor

This is either Mobile or Desktop. The form factor affects:

  • screen size and device pixel ratio
  • how the Lighthouse performance score is calculated (pages are expected to load faster on mobile than on desktop, so the same metrics will result in a different score)
  • the user agent
Form factor Size Device pixel ratio
Mobile 412x660px 2.625
Desktop 1350x940px 1

User Agent

Set a custom user agent header.

CPU throttling

This setting slows down code execution to simulate a device with a less powerful CPU.

Disable service workers

Don't register service workers. This can make it easier to test page performance if your service workers make a large number of requests to prefetch additional resources.

Block ads/tracking

This option installs uBlock Origin on the test device.

Still need help? Contact for support.
DebugBear is a website monitoring tool built for front-end teams. Track performance metrics and Lighthouse scores in CI and production. Learn more.