By Sarah E. Needleman

TikTok and WeChat may soon no longer be available in the U.S.

Downloads of the popular Chinese-owned apps will be banned as of Sunday night, the Trump administration said on Friday, citing national security and data privacy concerns. For TikTok, a full ban is expected to happen after Nov. 12, though discussions for a deal that would incorporate data safeguards could enable U.S. users continued access to the video-sharing app.

Video-sharing app TikTok is owned by Beijing-based ByteDance Ltd. WeChat, a messaging and electronic-payment app, is owned by Shenzhen-based Tencent Holdings Ltd.

The White House's decision comes after Oracle Corp. won the bidding for TikTok's U.S. operations, beating out Microsoft Corp., according to people familiar with the high-profile deal to salvage the social-media sensation. But on Thursday a new plan arose that would give Oracle as well as Walmart Inc. together a significant stake, people familiar with the matter said. Both U.S. and Chinese authorities, though, would have to approve the terms of the deal.

Here is more on what the latest developments mean for the future of TikTok and WeChat in the U.S.:

If I have TikTok or WeChat on my phone, will it be usable in the U.S. after Sunday night?

You will be able to use TikTok if it is on your phone already, but you won't be able to perform any payment functions in the U.S. on WeChat, according to the Commerce Department. U.S. authorities also could force Apple Inc. and Google to remove TikTok and WeChat from their mobile app stores, preventing new downloads and restricting current users from receiving software updates. Over time, that could diminish usability of the apps.

How will people be able to access TikTok?

Americans might have to become more like Chinese internet users, some of whom use virtual private networks and set their locations outside the country to get around China's national internet firewall, which blocks numerous websites, including Google and Facebook. Similar VPN workarounds could be an option for U.S. TikTok users.

But even if Apple and Google take TikTok off their marketplaces, experts say users could still access TikTok and WeChat through sideloaded apps, or ones that haven't gone through Google and Apple's verification processes. This method, however, could potentially expose users to security vulnerabilities and malware.

What are Apple and Google planning?

Apple and Google owner Alphabet Inc. didn't respond to requests for comment.

Are there other ways the U.S. could ban TikTok?

Avery Gardiner, general counsel at the Center for Democracy & Technology, said earlier this month Apple and Google could fight a government ban by saying that it restricts access to communication under the First Amendment. Such arguments have prevailed in censorship cases involving book publishers and newspapers, Ms. Gardiner said.

TikTok and a group representing WeChat users filed lawsuits in August challenging President Trump's executive orders issued on Aug. 6. In the filing, TikTok said it had taken vast measures to protect the privacy and security of user data in the U.S. and explained those efforts to the government in a security review. A Tencent spokesperson said Friday that WeChat was designed to serve international users outside of mainland China and has always incorporated the highest standards of user privacy and data security.

Has anything like this happened before?

The executive orders against TikTok and WeChat bar people in the U.S. or subject to U.S. jurisdiction from transactions on those two platforms. The president used a similar strategy last year in an executive order that effectively barred U.S. companies from buying telecommunications network gear and services from Huawei Technologies Co., the Chinese firm that makes phones, tablets and 5G equipment. As with TikTok and WeChat, the government cited national-security concerns. Experts say the U.S. case against Huawei was more easily understood because Huawei's transactions involve physical hardware and other equipment.

The forced sale of TikTok's U.S. operations is unusual because it appears to make it necessary for ByteDance to separate some pieces of the app's business geographically, presenting an unusually thorny technical challenge. For now, TikTokers may have to keep dancing to save their favorite app. Vanessa Pappas, who became the interim head of TikTok last month after CEO Kevin Mayer abruptly resigned, told The Wall Street Journal she aims to keep the platform open, inclusive and as a place for self-expression and community.

Are there other ways the U.S. could ban TikTok and WeChat?

Experts say the president's order could also thwart TikTok and WeChat by preventing other companies from engaging with the app or providing it with services, since the order targets transactions with the company. Like other social-media platforms, TikTok and WeChat use cloud-computing services and sell advertisements. If TikTok and WeChat were to have to rely on non-American companies for those services, it could have a substantial effect on the usability, speed and security of the apps. By attempting to cut off transactions between American companies and the platforms, the order also threatens TikTok and WeChat's advertising revenue from the U.S., experts say.

Sebastian Herrera contributed to this article

Write to Sarah E. Needleman at sarah.needleman@wsj.com