Reddit is opening an office in Chicago, the tech company's first outside the coasts.

The website, known for its massive community of that can make content go viral, is building out its advertising platform. There are major brands and advertising agencies with a presence in Chicago, and opening an office will give Reddit better access to that community, said Rob Sprungman, senior director of central brand partnerships.

"We need to be a part of the fabric of the marketing community here," said Sprungman, the first employee of Reddit's Chicago office. "The market has incredible talent ... but also some great digital tech we can pull from, as well as people moving here to be a part of it all."

Sprungman plans to work out of a co-working space as he builds up the Chicago team. He expects to have a permanent office and nine employees by the end of the year.

Launched in 2005, Reddit has built its user base to about 330 million active monthly users. Redditors, as the users are often called, subscribe to communities that discuss different topics and interests. Those communities are referred to as subreddits, and users can post or comment within each one. There are about 138,000 active subreddit communities. The topics they cover—from niche to general—are vast.

There's one called The-Donald ("a never-ending rally dedicated to the 45th President of the United States, Donald J. Trump") and one called Contagious Laughter ("videos and audio of people laughing infectiously"). There are Chicago-centric subreddits, and several on puppies.

When people post in a subreddit community, the other users know what they're talking about, Sprungman said. He pointed to a subreddit community on investment, in which people ask questions like what they should do with their 401(k) after a job change. That's not a question most users would take to another social media platform.

"It's the kind of community where brands can do something really interesting," Sprungman said.

Some companies are already tapping into Reddit's reach. Reddit is known for hosting sessions called Ask Me Anything, where users can pepper celebrities or participants with questions. To promote the new Audi Sport performance models, Audi and its advertising agency partnered with Reddit to host a live Ask Me Anything session in which actors Adam Scott and Elizabeth Banks took questions from Reddit users as they sped around a race track.

Opening an office in Chicago will give the social media platform better access to the companies it already works with, such as McDonald's and auto companies in Detroit, said Zubair Jandali, vice president of brand partnerships. It also will place it closer to brands and agencies it hopes to build relationships with, including those in dining, retail, consumer packaged goods and quick-service restaurants.

Reddit, which bills itself as "the front page of the internet," has made other moves to bolster its ad platform. It started rolling out a redesign to its users at the beginning of April, which Jandali said could make the site easier to navigate for new users and help grow existing communities. It also hired Time veteran Jen Wong as chief operating officer this month. Reddit said in an announcement on its blog that one of Wong's goals would be to help the company build out its offerings for advertisers.

The company also plans to roll out video advertising in the coming months. It launched video hosting for its users last year.

San Francisco-based Reddit employs more than 350 people, about 75 of whom are on the brand partnership team, Jandali said. That team is expected to grow 50 percent this year.

The privately held company announced its latest funding round of $200 million in July, which valued it at $1.8 billion. Advance Publications—which owns Reddit's onetime parent company Conde Nast—still owns a majority stake. Reddit declined to disclose financial information.

It makes sense Reddit is expanding its advertising platform, and longtime users likely won't be surprised, said Adrienne Massanari, an assistant professor in the Department of Communications at University of Illinois at Chicago who has written a book on Reddit culture.

Users are so passionate about the interests they discuss on the platform that they're like evangelists within the communities, she said. But they also can be suspicious of advertisers or other authority figures. Massanari said she has seen politicians or celebrities that host Ask Me Anything sessions face a poor reception because users felt a product or message was being pushed on them. Reddit users also tend to be passionate about privacy, which advertisers will need to consider.

"The brands have to be really aware of how they're engaging in the space," she said.