Elon Musk, a billionaire, decided to rebrand Twitter as X, but it may be difficult legally because Microsoft and Meta already own the intellectual property rights to that letter.

X is a candidate for legal problems because it is used and quoted in trademarks so frequently. The business formerly known as Twitter may also have trouble in the future defending its X brand.

According to trademark lawyer Josh Gerben, there are already approximately 900 active U.S. trademark registrations that cover the letter X across a variety of businesses, therefore there is a “100% chance” that Twitter will be sued over this.

On Monday, Musk changed the name of the social media platform Twitter to X and introduced a new logo that features a stylised, black-and-white rendition of the letter.

If other branding may lead to customer confusion, trademark owners who protect things like brand names, logos, and slogans that identify suppliers of goods, may claim infringement. The options for relief include monetary damages and prohibiting use.

Since 2003, Microsoft has controlled the X trademark in connection with communications regarding their Xbox video-game system. A blue-and-white letter “X” is covered by a federal trademark owned by Meta Platforms, whose Threads platform is a new Twitter rival. The trademark was registered in 2019 and covers industries such as software and social media.

According to Gerben, Meta and Microsoft are unlikely to file a lawsuit unless they believe their brand equity has been violated by Twitter’s X.

Requests for comments from the three businesses received no response.

When Meta changed its name from Facebook, it faced legal problems over intellectual property. It is facing trademark claims from virtual reality business MetaX and investment firm Metacapital from last year, and it has already settled one of those disputes over its new infinity-symbol emblem.

Other people could still claim the moniker “X” if Musk is successful in changing it.

“Given the difficulty in protecting a single letter, especially one as popular commercially as ‘X’, Twitter’s protection is likely to be confined to very similar graphics to their X logo,” said Douglas Masters, a trademark lawyer at the law firm Loeb & Loeb.

“The protection will be very limited because the logo lacks much distinctiveness.”

Earlier today, Insider claimed that Meta had registered an X trademark, and attorney Ed Timberlake claimed that Microsoft had done the same.