Time magazine began rolling out a redesign of its web and mobile sites Wednesday night in a bid to start punching in the same digital weight class as CNN, The Huffington Post and The New York Times.

The new site will introduce large native ad units that unfurl as readers scroll among editorial stories. Some traditional display units are also getting a refresh, with ads for Citi pulling elements from a smaller display unit on the left side to a large box in the middle of the page.

"We're rethinking the way ads should look," said Jed Hartman, group publisher of news and business at Time Inc., which includes Time magazine. Siemens, Advil and Citi are sponsors for the redesign, he added.

The new site will also includes a dizzying panoramic picture from the top of Manhattan's One World Trade Center. The image accompanies a 6,000-word magazine article on the tower as well as a digital documentary from Time's Red Border films. Advil sponsored the editorial package.

The rollout comes just days before Time's onetime mortal enemy, Newsweek, reintroduces a print magazine to newsstands. Newsweek went all-digital at the end of 2012, when Barry Diller's IAC/InteractiveCorp still owned the title, with the coverline "#LASTPRINTISSUE." Mr. Diller sold the magazine last August to IBT Media, which eventually decided to bring Newsweek back to the ink-on-paper game, albeit with far smaller circulation than before.

Time and Newsweek executives said the similar timing of their digital and print initiatives this week was a coincidence, but it helps frame publishers' dilemmas and changing priorities in the media business today.

Since April, Time has hired 35 people to fill digital roles across editorial, business and development. It's also increased its monthly unique visitors to 12.1 million in January, a 26% increase from the month a year earlier, according to ComScore. That doesn't include mobile visitors, which Time says comprise nearly half the brand's traffic. CNN's desktop site, by comparison, drew nearly 40 million unique visitors in January, according to ComScore.

The bulk of Time's revenue comes from print advertising and subscriptions, but the redesign aims to further expand its digital presence. "It was long overdue," said George Janson, managing partner and director of print for Group M, of the redesign. "There are going to be a lot of eyes on this to see how it actually materializes."

Time parent Time Inc. is spinning off from parent Time Warner in the second quarter, meaning the publishing company won't have thriving entertainment businesses to help shelter it during rough weather. Time is a key part of the company's strategy going forward, according to Time Editor Nancy Gibbs.

Newsweek, which has a significantly smaller web presence, is betting on print reader-revenue to fuel a resurgence. But many in the media business wonder how a modest digital publisher such as IBT can save the title after the failure of more grandiose efforts, like Newsweek's merger with The Daily Beast and installation of Tina Brown as editor.

Starting Friday, in any case, Newsweek will distribute 70,000 copies of its print edition at a cost of $7.99 per issue. That will be a far different business, both in revenue and in costs, than its final six months in print in 2012, when it averaged paid and verified circulation above 1.5 million copies and charged $4.99 on newsstands.

IBT Media is convinced it can turn a profit with this model, according to Jim Impoco, Newsweek's editor in chief. "Advertising will be icing," he said.

Ads from Mazda, Singapore Airlines, All Nippon Airways, Paradies, Seton Hall University and Oakland University will appear in Newsweek's first issue back in print, which will run 68 pages total. The magazine did not provide a count of ad pages by press time.

Newsweek attracted 284,000 unique visitors in January, according to ComScore, which said it did not have 2013 numbers for Newsweek.com. (Newsweek said its traffic is much higher according to several other sources and is disputing the figures with ComScore.)

Time's ambitions are unsurprisingly much larger. Ms. Gibbs described the new site as a "destination for 24 hours news coverage" that will also house multimedia elements and magazine features, the latter available to subscribers only. The site's three-column approach features a large middle section, which Time editors will populate with their must-read stories of the day, giving visitors a way to check in and see what's happening in the world, according to Ms. Gibbs.

"Time's site will be one of the most essential news sites," she said.

"Time matters," said Robin Steinberg, exec VP and director of publishing investment and activation at MediaVest. She welcomed the redesign, but cautioned that for advertisers, a magazine's digital presence also rests on its ability to deliver a targeted audience.

"If they're creating and delivering a richer, deeper and more attractive consumer experience, that's meaningful," she said. "But performance matters and could be more influential to advertisers."