Journalists at digital-news upstart Vox Media walked off the job for the day on Thursday in a bid to secure a new collective-bargaining agreement with the company.

The labor action was one of the most aggressive moves yet taken by a newly unionized digital-news company.

Vox — which includes the real estate site Curbed, the food site Eater, the sports site SB Nation and itself — is one of a number of digital-media operations whose workforces have voted to unionize in recent years.

Despite organizing last year under the Writers Guild of America East (WGA), however, Vox’s employees have not yet secured an agreement with management. Thursday was the final scheduled day of bargaining, which began in April of last year.

In a show of resolve, some 300 employees stayed out of Vox’s offices on Thursday, including its headquarters in Washington.

The walkout left, which specializes in news analysis, and its sister sites with little fresh content to post online. Vox’s only timely story was its lead — attributed only to “Vox Staff” — about President Trump’s Fox News interview in which he insulted House Speaker Nancy Pelosi (D-Calif.) and former special counsel Robert S. Mueller III while speaking at the American military cemetery in Normandy, France, for the 75th anniversary of the D-Day invasion.

The site made no mention of the staff walkout or explained the limited amount of news to its readers.

The Writers Guild has been seeking a contract that contains salary minimums, guaranteed annual cost-of-living increases, severance provisions and rules about the use of freelancers and subcontractors. As of late Thursday, a spokesman for the union, Jason Gordon, said, “It’s possible we’ll reach a deal, but we’re looking at all options if one isn’t reached.”

He declined to detail what those options are or to say whether employees will return to work on Friday.

In a statement posted on Twitter, the Vox employees’ bargaining committee said, “Today’s our last scheduled day of bargaining. . . . We’ve decided we’re not showing up to work today until we resolve these issues. Our unit members are taking their sites dark today to show management how important these issues are to us. Contract now.” The posts included photos of empty desks at Vox’s New York office.

Vox’s chief executive, Jim Bankoff, declined to comment. But in a memo to employees on Thursday he wrote that only a “handful of economic issues” remained to be resolved. “While I’m disappointed that the union chose to take this action in the midst of good-faith bargaining, especially as progress was being made, I am still committed to promptly resolving all outstanding issues,” he wrote, adding: “While paying people a lot more than market wages sounds great on the surface, it’s not realistic or smart.”

Several employees of the company tweeted complaints about Vox’s apparent strategy of filling out its websites by rerunning older stories they had written weeks earlier. “My byline on Eater NY today was not put up by me and [used] without my permission,” tweeted Eater Senior Editor Stefanie Tuder. “I join the @vox_union in a walkout for better wages and strong severance.”

Digital-media pioneers generally kept labor organizers at bay in their early years, despite low pay and difficult working conditions for a workforce that is mostly young. But since 2015, workers at many of the most popular digital sites — almost all of them located in high-cost cities such as New York and Washington — have unionized and reached contracts with employers.

The WGA, for example, now represents HuffPost, Fast Company, ThinkProgress, Talking Points Memo, the Intercept, Vice, Salon, Slate, MTV News and Gizmodo Media Group, among others.

Most of the digital companies still lose money — Vox, which is privately owned, is believed to have broken even last year — and several have had layoffs in recent months in an increasingly competitive environment for advertising.

The unionization wave, however, has raised minimum salaries, improved benefits and established work rules that were previously left to the discretion of managers. Importantly, the companies are based in cities with strong protections for union organizing.

Vox’s day-long walkout was bolder than other recent collective actions designed to jump-start stalled negotiations. Employees at Thrillist, which covers food and entertainment, walked off the job for a day last summer in an effort move negotiations along; workers at Vice, Gizmodo and Slate also authorized strikes but didn’t walk out. All four companies eventually came to an agreement with workers.