Selenium 4.8 breaks non-w3c compatability, including:

• non-prefixed vendor options

At the same time, chrome has adjusted its headless argument from -headless to -headless=new.

This is a meta issue to check all affected tooling.

This does not mean that we are moving to Selenium 4.8, just that we support it.

As it stands, this change does not break b/c with Selenium 3.9.1, because it's just dropping support for non-w3c changes.

We're now find to do this because MDL-66979, where we introduced our own W3C support, landed to 3.9+ in January 2021. It's supported in:

• 3.9.5+
• 3.10.2+
• 3.11.0+
• 4.0.0+

The changes we need to make are:

• stop using non vendor-prefixed extensions
• rename headless

It's worth noting that we couldn't do this at the time because we needed to support both W3C and non-W3C webdriver during a transition period. I think it's fair to say that we can drop this non-w3c support now. Whilst some released version of 3.9 are affected, I don't think it's unreasonable for us to ask people to use a newer version where this is already fixed instead.

Some references:

• https://www.selenium.dev/blog/2023/headless-is-going-away/
• https://developer.chrome.com/articles/new-headless/
• https://www.selenium.dev/blog/2022/legacy-protocol-support/