[electricmonk]

IANYL.

Microsoft owns a trademark registration for X [standard character] for certain goods and services (see: https://tsdr.uspto.gov/#caseNumber=2693757&caseSearchType=US...). Meta owns a trademark registration for X (Stylized), which Microsoft apparently assigned to Meta (see https://tsdr.uspto.gov/#caseNumber=87980831&caseType=SERIAL_...). Musk as been using X in various capacities since the 90s, and depending on the specifics of that use, may have some common law trademark rights in the mark.

Regardless of whether or not any party has a registration for a particular trademark/service mark identifying certain goods/services, the question about whether the marks should be allowed to co-exist depends on whether there is a likelihood that there will be confusion between the 2 marks in the marketplace (defining the appropriate marketplace is part of the test for any given likelihood of confusion analysis). There are some other concerns, such as dilution with respect to famous marks that may or may not come into play, but likelihood of [consumer] confusion is the root of it.

[CydeWeys]

Meta and Microsoft may have registered those trademarks but I haven't seen them using them, so they might struggle to actually defend them in court against someone who is very clearly actually using "X".

Honestly Apple probably has the best shot, as they do use "X" prominently. Mac OS X, iPhone X, etc.

[electricmonk]

IANYL.

Just because we haven't seen them doesn't mean there is a market (e.g., b2b) where they may be using them. Also, in this particular instance, since these are registered we can look at what they have provided the USPTO as evidence of use in order to renew the registrations. Microsoft (I think the X involved might actually be the X on the globe logo): https://tsdr.uspto.gov/documentviewer?caseId=sn76041368&docI.... For Microsoft's use before assigning to Meta: https://tsdr.uspto.gov/documentviewer?caseId=sn87980831&docI.... For that second one, looks like MS sold some assets to Meta after is shut down its Mixer service: https://en.wikipedia.org/wiki/Mixer_(service)

Apple does use X a lot in product names, but (i) the use is never on its own, so the comparison of the marks is, e.g., X vs Mac OS X, and (ii) Apple generally uses X to denote "10" so that portion of the mark is arguably descriptive or generic as a version number (see https://tmep.uspto.gov/RDMS/TMEP/print?version=current&href=...).

[nba456_]

MS has definitely been using it for Xbox and XCloud.

[kyriakos]

Isn't xbox logo an x?

[gorlilla]

The "Moron in a hurry test." is stikl one of my favorites.