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Firefox WebDriver Newsletter — 122

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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 122 release cycle.


With Firefox being an open source project, we are grateful to get contributions from people outside of Mozilla.

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.


The modifications outlined in this section are applicable to both WebDriver BiDi and Marionette, as both implementations utilize a shared set of common code:

WebDriver BiDi

New: Support for the “browsingContext.traverseHistory” command

The browsingContext.traverseHistory command enables clients to navigate pages within a specified browsing context backward and forward in history, similar to a user clicking the back and forward buttons in the browser’s toolbar. The command expects a delta number argument to specify how many history steps to traverse. For instance to jump forward to the next page, delta should be set to 1. To navigate back 3 steps – and therefore skip 2 entries – delta should be -3, as in the example below:

  "id": 68,
  "method": "browsingContext.traverseHistory",
  "params": {
    "delta": -3

Updates for the browsingContext.setViewport command

In preparation for the addition of emulating the device pixel ratio (DPR) in the browsingContext.setViewport command, a variant was needed to retain the current viewport size of the specified top-level browsing context. Using null as a value for the viewport argument, which is already supported, resets the view port to its original size. Omitting the argument instead ensures that the viewport size remains unchanged.

Bug Fixes

Marionette (WebDriver classic)

Bug Fixes

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