New Browser Simulation Parameters in the OnPage Lighthouse API

The OnPage Lighthouse API now supports a set of new parameters for browser simulation. You can now customize the browser environment used during Lighthouse audits to better reflect real-world device and network conditions.

What’s new

We added seven new parameters that allow you to set specific browser conditions for a Lighthouse audit, from a custom user agent to a network throttling profile:

• custom_user_agent – sets a custom user agent string for the browser used during the audit.
• browser_screen_width – sets the browser’s screen width to emulate a specific device.
• browser_screen_height – sets the browser’s screen height to emulate a specific device.
• browser_screen_scale_factor – sets the browser’s device pixel ratio.
• browser_network_throttling_method – defines the throttling method used during the audit. Can take the following values: simulate – calculates estimated performance metrics without applying explicit throttling; devtools – explicitly applies the throttling settings specified in browser_network_throttling and browser_cpu_throttling_multiplier; provided – uses the network conditions without applying throttling.
• browser_cpu_throttling_multiplier – sets the CPU throttling multiplier to a value between 1 and 4. Applied only when browser_network_throttling_method is set to devtools.
• browser_network_throttling – sets the network throttling profile. Possible values: no_throttling, fast_4g, slow_4g, regular_3g, pc. Also applied only when browser_network_throttling_method is set to devtools.

How it works

All new parameters are optional, except browser_cpu_throttling_multiplier and browser_network_throttling, which are required when browser_network_throttling_method is set to devtools. To use them, include the relevant parameter in your Lighthouse endpoint request payload. The browser_network_throttling_method parameter controls overall throttling, while the screen and user agent parameters adjust the browser environment independently.

Why it matters

Lighthouse scores can vary significantly depending on the device and network conditions under which the audit runs. These new parameters allow you to run audits that better reflect the experience of a real user. For example, you can run custom scenarios to simulate slow or fast connection speeds, the use of low-performance devices, and leverage this data to improve your website’s technical SEO. Additionally, you can integrate browser simulation options into your custom analysis tools built upon the OnPage Lighthouse API.

Check out the updated documentation for the Lighthouse API to get started.