The Web is poised for a comeback. How’s that? Isn’t the Web already the crucial utility of online commerce, information and entertainment? In many ways, it certainly is. The Web’s importance is indisputable — but there are signs that it is slipping. Investment, innovation and energy have been shifting elsewhere in computing — mainly, to shopping, gaming and news applications for smart phones and tablet computers.

These applications often tap into web sites for information on all manner of things. But they do not reside on the open Web, and cannot be searched and linked to one another in the same way web applications can. Think of the apps tailored for Apple’s iPhones and iPads, or those made for Google’s Android operating system. Social networking sites like Facebook and Twitter have similar characteristics, as walled gardens that are connected to the open Web but are separate from it.

This is the trend that Wired magazine described last September, under an intentionally exaggerated headline: ‘‘The Web Is Dead.’’ And Tim Berners-Lee, the Web’s creator, issued a warning in the December issue of Scientific American. ‘‘The Web as we know it,’’ he wrote, ‘‘is being threatened.’’ The danger, he added, is that ‘‘the Web could be broken into fragmented islands.’’

But the Web’s fortunes may soon brighten remarkably. The scenario relies on a collection of technologies, already years in development, that is starting to make its way into the mainstream of computing. HTML5 is the geeky umbrella term for this assemblage. (It’s the fifth generation of HyperTest Markup Language, which is the way Web pages are written in code.)

Engineers say the technology will make it possible to write Web applications, accessed with a browser, that are as visually rich and lively as the so-called native applications that are now designed to run on a specific device, like an iPad or an Android-based tablet.

The Web browsing software that is needed to bring HTML 5 to life has recently arrived. Last week, Mozilla, the maker of Firefox, released the newest version of its browser, showing off its support for the new technology. A week earlier, Microsoft brought out its new Internet Explorer tuned to run HTML 5.

The Safari browser from Apple, meanwhile, also supports the new technology, and the company has particularly embraced HTML5’s video-playing feature as an alternative to Adobe’s Flash player. And the Chrome browser team from Google has long been a leader in HTML5 development.

The technology, by all accounts, is an innovative achievement. HTML5 represents the ‘‘next big step in the progress of the Web,’’ says Jeffrey Jaffe, chief executive of the World Wide Web Consortium, which guides the development of technical standards. Paul Mercer, a veteran Silicon Valley software designer, says the technology will make it possible to ‘‘achieve the dream of expressive, interactive applications on the Web that are Cupertino-class,’’ a reference to the headquarters of Apple, where Mercer worked for years.

There are also potentially sweeping business implications, executives and investors say. The technology could alter the playing field in the emerging market for digital media and mobile applications, creating new market opportunities.

‘‘People are underestimating the power of the Web. I think we’re going to see an explosion of Web-based apps over the next couple of years,’’ says John Lilly, a venture partner at Greylock Partners, a venture capital firm in Silicon Valley.

Indeed, start-up companies like Zite and Flipboard present media content in magazine-style pages on the iPad, using HTML5. The free software from Flipboard, for example, taps a user’s online social networks for reading recommendations. Flipboard is also working with publishers, offering them tools for automating the display of pages on the iPad.  ‘‘You’re seeing this increasing move to HTML5 among publishers,’’ says Mike McCue, the company’s chief executive.

In theory, the technology could give publishers a powerful counterweight to Apple, the early dominant distributor of paid media content. Apple has leading devices in the iPhone and iPad, and media companies use its software to tailor their content for them. And the company’s App Store is the hub for retail distribution online.

Publishers flinched, though, when Apple announced in February the terms for digital newspaper and magazine subscriptions sold through its App Store: Apple will get a 30 percent cut and the customer information, unless a subscriber agrees to pass some of that data on to a publisher.

The 30 percent is the same that Apple collects on music and games sold through its store. Publishers had been pushing for better terms and sharing of customer information, because they would be selling continuing subscriptions instead of onetime transactions, like an individual song or an album.

Most major publishers are experimenting with HTML5 today. Yet even if HTML5 allows publishers to make applications that shine on the iPad without Apple's software, the distribution power of Apple won't necessarily decline. The company could still end up running the leading marketplace in online publishing sales if the iPad remains the runaway leader in tablet computing -just as the popularity of iPod music players has reinforced sales at the company's music store.

So far, publishers mostly plan to use the new technology to streamline digital development, thereby cutting costs. Ideally, they say, HTML5 would be the main technology used for all mobile programs, with some tweaking of applications on each device.

``If HTML5 lives up to its promise, that would make my life easier,'' says Joe Simon, chief technology officer at Condé Nast. The publisher has built dozens of iPhone and iPad applications in recent months for its 18 magazines, and will soon introduce Android applications for the Motorola Xoom for The New Yorker and Wired.

The rivalry between the worlds of the Web and native applications, analysts say, is set to play out over the next couple of years. There are strong advocates in each camp, even within companies. Google, for example, straddles the two worlds, with its Android team as well as its developers of HTML5 technology.

Sundar Pichai, vice president for product management for Google's Chrome browser, is betting on the triumph of HTML5. ``In the mobile world, the dominant model is native apps,'' Pichai concedes, but he adds that the real competition is just beginning. ``As these ecosystems evolve,'' he says, ``I think the incredible advantages of the Web will prevail.''