Javier Sanz recently decided his oDesk profile pic needed a fake beard.

ODesk is an online marketplace where you can find temporary or freelance work that you can do from home, with assignments ranging from web design to software programming to data entry. You build an online profile that details who you are and the work you've done, and the site helps match you with the right short-term gig, letting you contact employers – and letting them contact you.

Although he no longer uses oDesk, Sanz has spent a fair amount of time searching for work on the site, and this past fall, he ran a little test, Photoshopping a beard into his profile picture. He knew he looked a little young for his age, and he figured a beard would make him look older – and more trustworthy.

Sure enough, when he inquired about job openings as a bearded contractor, the response rate jumped from 12 percent to 35 percent.

Based in Belgium, Sanz specializes in online marketing, including search engine optimization, or SEO – the tricks that help you get your website noticed on the search engines run by Google and Microsoft. He believes that similar techniques will become increasingly important on new-age job markets like oDesk, which have become massively popular in recent years as employers eschew full-time employees in favor of farming out work to temps. It's not just about Photoshopping your profile. You can increase your chance of employment, he says, with countless other techniques.

>'I will try to spend time improving my profile before improving my newbie coding skills' Javier Sanz

ODesk – which recently merged with a rival job marketplace called Elance – is used by over 5 million contract workers, all battling to fill their schedules with short-term jobs. Sanz argues there are so many people on these sites, offering so many of the same basic job skills, that honing your profile is as important honing your talents. "If I ever come back to use these sites," says Sanz, who now has a full-time job, "I will try to spend time improving my profile before improving my newbie coding skills."

Yes, job hunters have spent years playing tricks with their resumes in order to catch the attention of employees. But at sites like oDesk and TaskRabbit – which automate job hunting at a massive scale – these tricks are moving into a whole new realm. Some workers are even turning to outfits like Workshop, which charges a monthly fee to help freelancers find gigs through online marketplaces.

ODesk CEO Gary Swart says the site is carefully designed to match the right worker with the right job. "One of our biggest challenges is ensuring that clients get the right freelancer," he explains. "We often refer to it almost as a dating site. There's lot of guys and girls out there, but they don't all go together."

This involves collecting a wide array of information about each contractor. "We look at everything we possibly can," says oDesk director of data science Ramesh Johari. The site tracks your past work experience, but workers can also take tests designed to measure certain skills, such as use of the English language or, well, Photoshop, and they can connect their to oDesk profiles to LinkedIn and GitHub to demonstrate experience from outside the site.

What's more, when a job is completed, both the worker and the employer can rate each other. The company tries hard to make its rankings fair: There's a mechanism for anonymous feedback, so neither side has to lose face by publicly trashing the other if a job didn't go well. Johari says the company can spot instances when there was a huge discrepancy between how a freelancer thought a job went and the way an employer thought things went, and adjust rankings accordingly.

But Sanz believes you can get far more work if you spruce up your profile in small ways – especially when you consider that, in many cases, jobs are completed remotely, so that you never meet your boss. They'll never know you don't have a beard.

Sanz also recommends taking hourly projects rather than longer gigs. That tends to produce more feedback and therefore better rankings than fixed rate contracts. But the most important thing to do, he says, is to stay active on the site. Long periods of inactivity will hurt your chances of showing up in search results. "They try to promote those profiles that have been active in the last few days, as it gives a higher probability to the employer to be answered," he says. "ODesk gives more relevance to those that have been working."

Some contractors are working to improve their profiles by farming out their jobs to someone else. Momchil Kyurkchiev, the co-founder of A/B testing company Leanplum, has seen this first-hand. Last year, he hired a data entry worker on oDesk with a five-star rating and over 1,000 hours of work under his belt, and it soon became clear that others were doing his work for him.

"Being entrepreneurial I understand," Krurkchiev says. "It looks like this guy is working really hard, but it's really just more people. By farming it out, he essentially parallelized it, which is really clever."

Swart says that this type of subcontracting is against the rules at oDesk, and that the company tries to verify the identity of its contractors. "We can even add a web camera so that you can make sure it's the contractor doing the work," he says. But oDesk does let external agencies advise job hunters on how to hone their profiles.

ODesk's CEO insists that there is more than enough work on the site to go around, and that freelancers shouldn't worry so much about gaming the system. But this is the internet. As these marketplaces continue to grow, so will the battle to rig them.