SAN FRANCISCO >> Joining the battle to redefine Internet search, Yahoo is taking aim with a new browser enhancement it calls “Axis.”

It alters browsers made by other companies to display search results in a more convenient and visual format.

The troubled Internet company Yahoo Inc. released Axis in Apple’s app store late Wednesday. That version will work only on Apple’s iPhone, iPad and iPod Touch. The software also can be installed as a plug-in on most major browsers used on desktop computers and laptops. Apps for other mobile devices are in the works. 

A device running Axis can display search results in a panorama of visual thumbnails that can be scrolled through above a Web page. It’s a departure from search engines’ traditional presentation of a list of staid Web links that require more navigation and guesswork.

“Searching through links has outlived its utility,” said Shashi Seth, a Yahoo Inc. senior vice president. “Users are demanding more now because we are all short on time.”

All the major search engines are adopting new formats intended to make it easier for users to find information without clicking through to page after page.

Two weeks ago, Microsoft Corp. previewed an upcoming change that will spread Bing’s search results in three columns, including one devoted to personalized recommendations pulled from Facebook, Twitter and other social networking services.

Last week, Google unveiled a new search feature called a “Knowledge Graph” that seeks to provide more immediate answers by highlighting information from a database containing more than 500 million entries about people, places and other commonly requested things.

The biggest challenge facing Axis may be overcoming the perception that Yahoo stopped innovating in search when it joined forces with Microsoft and started relying on Bing.

“If it’s good enough and cool enough, people will go out of their way to get it,” predicted IDC analyst Karsten Weide.

Yahoo is counting on Axis to reverse its steadily declining share of the Internet’s lucrative search market and bring it more traffic from among the growing number of smartphone and tablet users.

Its greatest appeal figures to be on mobile devices because users with the app installed can see their search results at the top of the screen just by flicking on whatever page is displayed. The relevant results appear in a ribbon of Web page snapshots, making it easier for users to find the right information.

Much like Google’s Knowledge Graph, Axis draws its results from a custom-built index. Most of the data in the Axis index resides on Yahoo’s own services. If Axis can’t find answers there, it presents links from Bing’s search index.

Yahoo has relied on Bing’s technology since 2010 as part of a decade-long partnership formed to lure users away from Google. So far, most of Bing’s gains have come at Yahoo’s expense, but Yahoo was losing search traffic well before it began leaning on Bing.

Yahoo’s share of the U.S. search market stood at 13.5 percent through April, down from nearly 25 percent five years ago, according to the research firm comScore Inc. Bing holds a 15.4 percent share, up from 9.4 percent five years ago when Microsoft operated a search engine under a different name and system. Google’s share has climbed from 56 percent five years ago to more than 66 percent now.

Yahoo’s alliance with Microsoft gives it the flexibility to offer unique search features, such as Axis, that Bing doesn’t have. Getting people to use its search engine more frequently is important to Yahoo because it keeps 88 percent of the revenue generated from requests made on its service, but none when a query is entered directly on Bing.

The erosion in Yahoo’s Internet market share has been a major factor in a financial malaise that has caused the company’s stock to slump for years and contributed to the management turmoil that has taken Yahoo through four CEOs — including two interim leaders — during just the past nine months, when it was working on Axis.

Yahoo won’t show ads next to Axis search results initially, but the company believes the visual format will be ideal for video commercials and graphical marketing.

In an effort to make Axis even more useful, Yahoo plans to store search activity on its servers so users can have access to their past activity on any computer or mobile device where they log in. Axis will accept the logins that people use on Google and Facebook, as well as Yahoo.