Graphics of Facebook pages created by a Russian troll factory are displayed during a congressional hearing. (SHAWN THEW/EPA-EFE/REX/Shutterstock)

Facebook and Twitter forged ahead Thursday with new efforts to disclose more information about the political advertisements that appear on their sites, part of a broad campaign to help users better understand why they see the content they do and who’s behind it.

For both tech companies, the stakes are high ahead of the 2018 midterm election, two years after Russian agents spread propaganda – through ads and other posts – on social media sites in a bid to create social and political unrest in the United States during the 2016 presidential race.

Starting Thursday on Facebook, political ads will include a marker at the top indicating who has paid for it. Clicking on the label will bring users to a new repository of all political ads that have run on the site, along with information about the people who saw it, like their age and location. The new rules cover ads about political candidates as well as hot-button policy issues, like gun control, immigration and terrorism, and apply to both Facebook as well as its photo-sharing app, Instagram.

For example, Facebook data reflect that there are more than 4,200 active political ads promoting posts from the official page for President Trump. The archive includes ad purchases since May 7.

“Our intent is trying to help people understand who is trying to influence them on political and social issues, and why," Katie Harbath, Facebook's global politics and government outreach director, said on a call with reporters Thursday.

Twitter, meanwhile, said Thursday that it soon would require political advertisers to prove their identity before promoting tweets on the platform. In a blog post, the company said it also plans to label political ads “in the near future,” a promise it first made in October. Twitter said it is developing a separate policy for “issue ads,” the kind of content that Russian agents used on topics such as immigration and gun control.

Along with Facebook and Twitter, Google previously has promised more transparency around political ads that appear in search results or on sites like YouTube. Earlier this month, the search giant said it would begin verifying the identities of advertisers at the end of May, with a fuller database and report on political ads still to come.

By implementing these changes on their own, Facebook, Google and Twitter are trying to stave off tough new regulation from Washington, where lawmakers long have argued that the tech industry hasn’t done enough to police the content that appears online. Recently, members of Congress have demanded that major social media sites do a better job combating terrorist propaganda, removing hate speech and ensuring their powerful algorithms aren’t biased against conservatives – but it’s Russian disinformation that’s worried lawmakers most.

On Facebook alone, ads purchased by the Kremlin-aligned Internet Research Agency reached roughly 10 million U.S. users around the presidential race. Content from the IRA’s profiles and pages may have been seen by more than 140 million users on both Facebook and Instagram. And these Russian trolls similarly took their messages – stoking cultural, racial or political tensions – to Google-owned YouTube and Twitter during the 2016 election.

Despite calls for reform, Facebook’s changes have not been without controversy. Last week, the social giant said it would apply its new political ad label even to stories from news outlets about political subjects. That sparked an outcry from publishers, including the News Media Alliance, an advocacy organization representing The New York Times, The Wall Street Journal and The Washington Post.

On Thursday, though, Facebook acknowledged in a blog post that “news coverage of elections and important issues is distinct from advocacy or electoral ads, even if those news stories receive paid distribution on Facebook.” It said it would work with “news partners” to “help differentiate between news and non-news content.”