Keith Gormley wasn't looking for a new job on a day last fall when he used his iPhone to pull up the Indeed.com job-search app during his morning commute.

'I was bored, and maybe Twitter wasn't as active as usual. I was just flipping through to see what jobs were out there,' he said.

A social-media position at Prudential Financial Inc. caught Mr. Gormley's eye. He clicked through to the financial-services firm's career site, then did some research on Twitter and LinkedIn. A few days later, he applied for the job from his home computer. By December the 31-year-old had been hired.

Technology-research firm IDC has predicted that mobile devices will overtake desktop and laptop computers as Americans' preferred method for accessing the Internet by 2015. And as Web traffic migrates to smartphones and tablets, employers are rushing to develop mobile versions of their career websites, apps with interactive career content such as games and workplace tours, and simplified versions of job applications that can more easily be completed on a hand-held device.

Companies and recruiting experts believe mobile recruiting will help them engage candidates who may otherwise fall through the cracks: lower-wage and younger workers who may not have computers at home but are glued to their smartphones, as well as the coveted passive candidates -- people like Mr. Gormley who are already employed -- who might casually explore their options while they are off the clock.

'People are getting used to going online while sitting on a bus or waiting for an airplane. And if you hate your job, it's so easy to pull out your phone and see what else is out there,' said Cindy Cloud, seniormanager of employment-branding and marketing at Informatica Corp., a Silicon Valley data integration firm. 'We think mobile is the next big area for recruiting.'

'Any company that hasn't started to address mobile recruiting is at least a year behind,' said Elaine Orler, an expert in recruiting technology and president of the Talent Function Group, a human resources consulting firm. 'This is the connectivity that job seekers expect now.'

That may be, but it isn't widespread just yet. In January, iMomentous, a developer of mobile career sites, found that 167, or 33%, of Fortune 500 companies had career portals that were optimized in even the most basic way -- that is, sized to fit a smartphone screen. Still, it was an improvement over a year earlier, when 65 companies had mobile optimized career sites.

The biggest challenge is creating a streamlined user experience. After all, filling in dozens of fields and taking assessment tests is annoying enough with a traditional keyboard; it is even more cumbersome with a tiny screen and touch-based keyboard.

McDonald's Corp. tried to simplify the application process for mobile job candidates. While the mobile application asks for the same information as the desktop one -- both versions take 30 to 35 minutes to complete -- more than 30 fields were altered to provide dropdown menus rather than free-text boxes, and calendars were added that automatically populate queries in the correct format.

'With the hiring volume we have, it's much easier when someone comes into a restaurant and can apply right there on a phone instead of filling out a paper application,' said Nicholas Statler, director of employmentstrategy at McDonald's. It also cuts down on the time managers spend on new applicants since the managers no longer need to input all the information into a computer.

When the restaurant chain launched its first mobile career site in 2008, three million people visited it and 24,000 people used it to submit applications, said Mr. Statler. By 2012, those figures had jumped to 30 million visits and two million applications. Now, it brings in a little over 10% of total applications.

This development isn't just about technology. Friction in the labor market -- the phrase economists use to describe inefficiencies in matching employers with people looking for jobs -- might be eased if companies with low-skill, high-turnover jobs make it easier for job seekers to find and apply for openings, said Richard Freeman, a labor economist at Harvard University who has studied online job markets.

Firms are finding that, for higher-skilled positions too, candidates now expect the easy access of mobile job-searching and applications.

Macy's Inc. developed its first mobile optimized career page in 2011 to target 700 hires like software developers and marketers it was making for its e-commerce group. Only after that experiment worked did it roll out a mobile page for hourly workers, in 2012, said Michelle Cantor, director of employment process and jobs.com. Today, 20% to 25% of all applicants to Macy's apply on mobile devices.

This development goes hand in hand with two other transformative technology trends: social networking and cloud computing.

A February 2013 report from market-research firm Nielsen found that 63% of Americans access social-networking sites like LinkedIn or Facebook on their mobile devices. With job opportunities shared widely across these sites -- and recruiters relying on them to reach out to prospects -- more candidates are hearing about openings on their phones and tablets.

'If our recruiters send a message via LinkedIn, we know it's likely they're going to get it on their phone,' said Brett Underhill, director of recruiting programs at Prudential.

Employers are also starting to experiment with the next frontiers of mobile recruiting: using QR codes and text-messaging, two capabilities that are specifically geared to smartphones.

McDonald's and Macy's are both integrating QR codes into their hiring ads, so that job seekers or customers can walk into a store, scan the code they see on a poster, and be sent directly to the openings available at that location. With text messaging, applicants can text a phone number listed, for example, on a bus advertisement and immediately receive a link to job openings.