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]

Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.

[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.

[rhn]

For anybody else that stumbles upon this thread: Try double clicking the title bar close to the colored buttons.

It works for me on Firefox/Librefox and other apps that dont support it elsewhere on the titlebar.
Don’t hit the buttons themselves, just double click near them like right above or below a few pixels.

[Funkymonkeygin]

@rhn It only works if in the setings you use "zoom" but doesn't work if it is set as "maximise" which is the issue @gavro is rightly raising.

So yeah it's partially working but only when the system settings are on "zoom" it should also work when on "fill" mode

[Jd3891]

+ is also a relevant problem             

[denisw]

This was reported as a bug here: https://bugzilla.mozilla.org/show_bug.cgi?id=1928041

[aleonav]

fixed on macos27!

[Funkymonkeygin]

A little bit off topic but, you already have macos 27? I still can't update and only see the 26.5.1 version...

[aleonav]

you gotta join the apple developer program on their website, and then youll see a dev beta. Being dev its not guaranteed to be the most stable (iphone mirroring doesnt work for me) but besides from that its pretty good rn.

just look up how tog et it and enroll in the program and u should be able to see it under the beta settings

[gavro]

@Funkymonkeygin he's probably running the beta. it's opt-in but isn't recommended to do so on your primary work machine, as it is not considered stable yet.

[Funkymonkeygin]

Thanks @gavro , it's then too early to say it's corrected on golden gate yet.

But glad that they worked on vidual issues that were awful on Tahoe.

[aleonav]

@Funkymonkeygin @gavro 
yea i am, i wrote a reply but I guess it didn't upload. It is a developer beta so you have to enroll in apple's developer thing on their site, but being a dev beta its not guaranteed to be as stable as public ones and you also can't roll it back w/out wiping your system. 

So far things seem to be pretty stable though (except iphone mirroring not working at all), but this issue w/ firefox is fixed in the update.