Double click on Title bar doesn't fill screen/macOS

[gavro]

In the Desktop & Dock settings on my mac i have set `Double-Click a window's title bar` to `Fill`, and it works not only with native applications, but others as well, for example Discord, Chrome etc. I am not a macOS developer so I don't know if there are any obstacles that prevent this feature from being added, but i use it very often, and it is a bit annoying that Firefox doesn't support it.
For reference I am using an Apple Sillicon MBP with Sequoia 15.6.1, and Firefox 15.6.1.

Note: I know there is a keyboard shortcut for doing this, but I am used to double clicking the title bar when adjusting my windows across the screen.

[Jon]

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[azguy]

gavro thanks for posting this!

I can confirm that the issue exists on every Mac with Mac OS 15+.

The Fill option was introduced September 2024. Unfortunately, Mozilla hasn't seemed to notice the new option and hasn't been supporting it.

[SirPirilin]

I’m experiencing the same issue on macOS 26.0.1 (25A362) using Firefox 144.0.2 (aarch64).

When double-clicking the title bar, the window doesn’t maximize, even though the system setting is set to “Zoom” or “Fill.”

I’ve noticed that Firefox, along with a few other apps, doesn’t perform this action, while some third-party applications, such as the ChatGPT app, do. Therefore, I believe this isn’t a macOS limitation but rather a missing functionality in Firefox.

Please, developers, fix this for us. It’s frustrating not being able to maximize the window with a double-click, especially since this gesture improves productivity.

Thank you, @gavro, for opening this topic.