WebDriver is a remote control interface that enables introspection and control of user agents. As such it can help developers to verify that their websites are working and performing well with all major browsers. The protocol is standardized by the W3C and consists of two separate specifications: WebDriver classic (HTTP) and the new WebDriver BiDi (Bi-Directional).

This newsletter gives an overview of the work we’ve done as part of the Firefox 138 release cycle.

Contributions

Firefox is an open source project, and we are always happy to receive external code contributions to our WebDriver implementation. We want to give special thanks to everyone who filed issues, bugs and submitted patches.

In Firefox 138, several contributors managed to land fixes and improvements in our codebase:

• Liam (ldebeasi) updated the browsingContext.Info type to include a clientWindow property.
• Spencer (speneth1) enabled preferences required to pipe logs to stdout.

WebDriver code is written in JavaScript, Python, and Rust so any web developer can contribute! Read how to setup the work environment and check the list of mentored issues for Marionette, or the list of mentored JavaScript bugs for WebDriver BiDi. Join our chatroom if you need any help to get started!

General

New: --remote-enable-system-access Firefox argument

A new Firefox argument, --remote-enable-system-access, was added to enable sensitive features, such as interacting with Browsing Contexts in the parent process (e.g., Browser UI) or using privileged APIs in content processes. This will be used for WebDriver BiDi features in the next releases, and can already be used with Marionette (see the Marionette section below).

Bug fixes:

• All remote protocols now enable the preferences required to properly pipe logs to stdout.

WebDriver BiDi

Updated: webExtension.install command now installs web extensions temporarily

The webExtension.install command now installs web extensions temporarily by default, allowing it to be used with unsigned extensions – either as an XPI file or as an unpacked folder. A new Firefox-specific parameter, moz:permanent, has been added to force installation as a regular extension instead.

Updated: browsingContext.setViewport command now supports userContexts

The browsingContext.setViewport command now supports a userContexts parameter, which must be an array of user context (Firefox container) ids. When provided, the viewport configuration will be applied to all Browsing Contexts belonging to those user contexts, as well as any future contexts created within them. This parameter cannot be used together with the existing context parameter.

Updated: browsingContext.Info now includes a clientWindow property

The browsingContext.Info type now includes a clientWindow property corresponding to the ID of the window owning the Browsing Context. It is typically returned by browsingContext.getTree or included in the payload of events such as browsingContext.contextCreated.

Marionette

Updated: --remote-enable-system-access required to use chrome context

Switching to the chrome (parent process) context with Marionette now requires using the --remote-enable-system-access command-line flag when starting Firefox.