LinkedIn is so 2011.

In the red-hot market for skilled software engineers, companies looking to make great hires are discovering that relying on traditional services that showcase candidates' work histories -- but not their actual work -- is a great way to miss out on the best available talent.

These days, there's a new game in town -- GitHub, a place where hiring managers and recruiters alike are increasingly turning to find not just the potential employees who look best on paper, but the ones that actively (and publicly) demonstrate their capabilities.

Last month, Andreessen Horowitz, one of the hottest venture capital firms in Silicon Valley, put $100 million -- its largest-ever investment -- into GitHub, a company built to facilitate the organization of open-source projects, and that makes money by selling licenses to commercial and corporate users.

Asked why his VC firm ponied up the nine figures, partner Ben Horowitz cited GitHub's dominance these days in being a central repository for open-source code. But he also touted the company's growing role as a place to find top-tier tech talent -- and, more to the point, a preferable alternative to LinkedIn.

"I was talking to my friend [who] runs a tech screening process for looking at engineers," Horowitz told CNET. "I said, 'What do you use for recruiting?' He said GitHub. I said why not LinkedIn? He said, 'why would I look at their resume when I can look at a body of work?' And since he said that to me, I ask everybody [what they use] for engineer recruiting, and everybody uses GitHub. That's a big deal. It means if you're an engineer and you don't use GitHub, you don't exist."

Every engineer and all the code

In Horowitz's view, GitHub has become a place where the hottest engineers are coming together to share their code, and as a result, the service is home to the most important project and collaboration tolls, as well as application life cycle management systems in the business. "They've got the ultimate advantage," Horowitz said, "because they have every engineer and all the code."

This assessment is shared widely throughout the tech industry. From small startups to established, household name powerhouses, GitHub is now seen as the go-to place to spot quality talent. To be sure, there are still engineers who will get Silicon Valley jobs without putting up a GitHub profile, and for whom LinkedIn is still an employment lifeline, and every company's mileage may vary, but a common view is that a developer who has a profile there has an advantage over those who don't.

At many companies, the feeling is that engineers who take the time to develop a GitHub profile and put in the energy to participate actively in the community can be better evaluated in advance than others.

"It's an excellent opportunity to see what they are passionate about, their coding style -- good or bad -- and fun side projects," said Will Young, director of Zappos Labs. "We love when developers see a need and just go ahead and code a solution to share with the community. We are looking for some amazing problem solvers on our team. This is hard to get from an interview or resume. But sometimes, we see someone's GitHub library and think, 'Wow, that is really cool and handy.'"

GitHub itself has been looking to its own service's community for talent, sometimes hiring people that may not present the most stellar picture on paper, but who show off stellar programming skills in real life. "Previously, where you went to college was the be all and end all," said Zach Holman, who evangelizes for GitHub. "The fact that that's not true anymore is fascinating."

Holman also said that internally, GitHub is seeing more and more signs that outside companies are using the service as an initial indicator of whether a potential hire is good or not. "Whether or not somebody has contributed to open source is a good indicator of whether they're a good engineer," he said.

Distinguish themselves

What's particularly attractive to the people who work at GitHub, Holman added, is that the service has become such a great way for developers to distinguish themselves, even as it got its start more as a place where people were sharing their work for no reason other than to do so.

But that sense of selflessly participating in open-source projects is something that is increasingly attractive to hiring companies. "I've heard some of our portfolio companies mention the number of [GitHub] contributions people make and how active they area, and connecting that with their credibility in the community," said Craig Driscoll, recruiting partner at Highland Capital Partners. "There's just the signaling that someone using those types of communities is a general type of qualifier...[especially the] frequency and quality of the contributions."

Indeed, some tech companies are turning to GitHub to identify potential new hires who aren't even actively looking for a new job, and who may not have a resume online. Of course, almost anyone getting hired is still going to have their resume checked out and their education scrutinized, and recruiters are still combing LinkedIn's millions of active users, but their GitHub presence may be the single-most important factor. "We're always looking for people who have forked a lot of [open-source] projects and contributed back into those projects," said Tim Milliron, director of engineering at Twilio, a developer of cloud-based communications apps. "We like people contributing into open source...That carries a lot of [weight with] us."

Milliron said that Twilio has been looking at GitHub as a recruiting platform for more than a year, but that the pace of doing so has accelerated significantly in the last six months. "If we look at 20 people and five have GitHub profiles," he said, "and one has [contributed a lot], then that person tends to bounce to the top of the list."

To be sure, GitHub is hardly the only open-source community that is being looked at by companies searching for technical talent. But in talking to people throughout the technology industry, it appears that GitHub is getting the lion's share of the attention. As Barney Pell, CEO of QuickPay, and the founder of Powerset, whose technology became the basis of Microsoft's Bing, put it, "Online open-source communities like GitHub bring large numbers of...developers together and are thus a natural place for recruiting."

CNET's Paul Sloan contributed to this report.