Elon Musk has posted a series of explicit tweets about Mark Zuckerberg, including This week, Mr Musk tweeted that “Zuck is a cuck”, and followed it up with a post in which he proposed a “literal dick measuring contest”, alongside a ruler emoji. On Monday, he then responded to a post in which another user speculated that Mr Musk would lose such a contest. “This would so inappropriate & lacking in dignity … let’s do it!!!” Mr Musk wrote in a reply. It is just the latest in Mr Musk’s often intense responses to the launch of Threads, a Twitter competitor launched by Mr Zuckerberg’s company, Meta. He has also threatened to sue Meta over the similarities with his app, suggested that it is falsely joyful, and boosted posts that suggested the launch of Threads had actually helped the launch of Twitter. Mr Musk has also attempted to suggest that Twitter is both free of censorship and the pressure to be happy. “You are free to be your true self here,” he wrote in his most recent post on the topic. He has also promoted a post from Twitter’s chief executive, Linda Yaccarino, in which she suggested that Threads’ success had actually helped Twitter’s growth. “Don’t want to leave you hanging by a thread… but Twitter, you really outdid yourselves!” she wrote. “Last week we had our largest usage day since February. There’s only ONE Twitter. You know it. I know it.” It is not clear how much the launch of Threads has boosted or hurt Twitter’s usage. But external estimates suggest that the site’s usage is “tanking”, according to experts. Meta’s Threads surged past 100 million signups in its first five days, according to Mark Zuckerberg. In doing so, it became the fastest online platform to hit the milestone, overtaking ChatGPT. The app has been setting new records for user additions since its launch on Wednesday, with celebrities from Jennifer Lopez to Kim Kardashian joining the platform seen as the first serious threat to the Elon Musk-owned microblogging app. Twitter has responded by threatening to sue Meta over the app, alleging that the social media behemoth used its trade secrets and other confidential information. That claim, legal experts say, could be hard to prove. Threads shares some resemblance to Twitter, as do the numerous other social media sites that have cropped up in recent months. It allows posts that are up to 500 characters long and include links, photos and videos of up to 5 minutes. The app’s sprint to 100 million users was much faster than the two months OpenAI-owned ChatGPT took in January, which had made it the fastest-growing consumer application in history, according to a UBS study. Still, Threads has some catching up to do. Twitter had nearly 240 million monetizable daily active users, according to a company statement in July last year. Additional reporting by Reuters Read More Twitter gets strange endorsement from Taliban over rival Threads Tucker Carlson’s Twitter show is haemorrhaging viewers, reports says Twitter traffic ‘tanking’ after record-breaking Threads launch SpaceX smashes reusable rocket record as Elon Musk makes bold Starship claim Twitter restores TweetDeck’s old, ‘better’ version – but for how long? Account tracking Elon Musk’s jet is now on Threads after Twitter suspended it