As a potential TikTok ban looms, millions of U.S. users are left wondering what could happen to both their app and accounts if the ban takes effect in just a few days.   The ban law, which passed Congress with wide bipartisan majorities and was signed by President Biden last April, gave TikTok until Jan.19 to either divest from ByteDance, or face a ban in the U.S.  TikTok has not publicly announced what users could expect on Sunday should the ban go into effect, though cybersecurity experts agree the ban does not necessarily mean the app will suddenly disappear from U.S. devices right as the clock strikes midnight.   The ban hinges on a decision from the Supreme Court, which took up TikTok’s challenge to the divest-or-ban law on an expedited timeline. The high court heard oral arguments last week and signaled sympathy with the government’s national security concerns with TikTok’s Chinese parent company, ByteDance.   Here’s what might happen if the ban goes into effect Sunday:   TikTok no longer offered on app stores, becomes buggy for existing users   The divest-or-ban law, formally known as the “Protecting Americans from Foreign Adversary Controlled Applications Act,” makes it illegal for U.S. app stores — like ones operated by Google or Apple —  and web-hosting services to distribute TikTok to its users.   As a result, the application will be pulled from app stores and unavailable for new downloads.   Still, existing downloads are not likely to be removed – at least initially – on U.S. devices.   "TikTok could do nothing and if the app store removes service — removes the ability to download the app — it won’t immediately cause a problem for most users,” said Jason Kelley, director of activism for digital rights non-profit Electronic Frontier Foundation.  But with no updates coming from app stores, the app will likely become more buggy and eventually nonfunctional for U.S. users.   “The bugs would come from the fact that TikTok could overnight, or over the course of multiple weeks or months, sort of slowly phase off service,” Kelley said, adding, “If I was going to take a bet, it’s that we see in 48 hours, most users will see just some sort of connection error when they go to load TikTok.”   These errors could include visuals failing to load, the inability to click links or see content posted after the ban takes effect, Kelley said.   TikTok immediately shuts off app in US While TikTok has not publicly confirmed its plans, one report claimed the company intends to immediately shut off its app for U.S. users on Sunday.   Unless the Supreme Court strikes down the ban, TikTok is planning to make the app unusable for people in the U.S. once the ban takes effect, The Information reported Tuesday, citing two people familiar with TikTok’s plans.   Under the plan, users trying to open the TikTok app will be greeted with a message directing them to a website with information about the ban, according to The Information report. Users will be given the option to download their data but will not be able to use the app, the outlet added.   TikTok’s lawyer, Noel Fransico, told the high court last week the platform will “go dark” unless the justices step in ahead of the deadline.   “They could choose to exit the market over concern of the impact,” Jennifer Huddleston, a senior fellow in technology policy at the Cato Institute told The Hill.  TikTok did not immediately respond to The Hill’s request for comment on the report or its plans for Sunday.   Users try VPNs  Cyber experts are predicting many users could attempt to use a virtual private network (VPN) to hide their IP address and access the app.   “What could happen is people will try to download a new version of TikTok, because the one on their phone no longer functions, and they can’t get it through the app stores,” Kelley said.   Using a VPN or alternative channel does not come without risks, Kelley noted. He predicted black market websites or hackers could try to take advantage of the influx of people searching how to download TikTok under the ban.   “The concern I would have people consider is if you can’t download the app itself from a reputable source, are you downloading an app that has been manipulated in some way?” he said. “I think that could be a potential outcome that people end up with a piece of spyware on their phone.”  “It’s going to...make it more likely if you’re trying to find an access point to the software, that you are going to end up with something that isn’t actually TikTok and something that’s potentially dangerous,” he added.   A rush to alternative apps   Cutting off access to an app used by more than 170 million Americans is likely to prompt TikTokers to seek replacements for the platform they have used over the past seven years.   The influx to alternative apps already started this week. The Chinese social media app Xiaohongshu surged to become the most downloaded free app on Apple’s App Store in the U.S. on Tuesday.   The Chinese app, which translates to “Little Red Book,” in English,” offers short video, posting and e-commerce abilities. The app rose to popularity in China and other regions in recent years and now boasts more than 300 million monthly active users.   Thousands of U.S. users joined Xiaohongshu earlier this week, dubbing themselves “TikTok refugees” in protest of the looming ban. Many of these American users were observed interacting with users apparently based in China, who were teaching Americans how to navigate the app and switch the language from Mandarin.   Lemon8, another ByteDance-owned app, also climbed the charts for downloads this week. The app has features similar to other popular apps, offering a photo or carousel photo upload like Instagram and a personalized video component like TikTok.   Despite the early excitement about these apps, it’s unclear whether they will eventually face the same challenges in the U.S. or if users will want to stick with them long-term.   The divest-or-ban law only applies to TikTok and ByteDance and its subsidiaries, meaning Lemon8 is likely to face similar challenges, but not other unrelated platforms.  Nonetheless, Mark Montgomery, the senior director of the Center on Cyber and Technology Innovation, said the law will help pave the way for future challenges to foreign-adversary-owned apps to move quicker.   “I feel good the TikTok thing is being handled the way it is. I remain concerned that there’s broader, persistent information operations attacks against the United States by our adversaries that generally go unacknowledged,” he told The Hill.   TikTok eventually divests  Even if the ban goes into effect, this does not prevent TikTok from divesting from ByteDance in the future.   Numerous companies and billionaires are rumored to have an interest in purchasing the social media platform and President-elect Trump, who will be sworn a day after the ban takes effect, has indicated he wants to find a solution to keep TikTok active in the U.S.   Still, a divestiture deal could take more than just a few days.   “This would be a sizable transaction, sizable transactions usually take some degree of time,” Huddleston said. “Yes, they can happen very quickly but even if there is a buyer, it’s usually not an overnight thing.”  “This is also occurring at a time where there is a lot of scrutiny of tech acquisitions,” she continued, likely referring to anticompetitive scrutiny major technology companies have faced in recent years.  Biden does have the option to extend the ban by 90 days before leaving the White House, but this requires ByteDance and TikTok to demonstrate divestiture negotiations are making progress.   Huddleston noted Trump, once in office, could also look to his congressional allies to pass legislation to extend the deadline.