Facebook is trying to alert some U.S. users that they fell victim to Russian propaganda during the 2016 presidential election.

In the coming weeks, the social giant plans to roll out a new tool so that users can check if they followed or “Liked” pages and accounts — on both Facebook and Instagram — that the Kremlin quietly set up over the past two years in order to sow social and political unrest, the company announced Wednesday.

Only a slice of the roughly 140 million users who may have seen Kremlin-backed content on Facebook and Instagram during the 2016 election can take advantage of Facebook’s new portal, which will soon become part of the site’s Help Center. That’s due in part to technical limitations, the company contends.

But the move nonetheless comes as the tech giant tries to assuage its critics in Congress while further working to “protect our platforms and the people who use them from bad actors who try to undermine our democracy,” Facebook said in a blog post Wednesday.

Over a two-year period around the 2016 election, Facebook said that about 29 million U.S. users directly saw content in their News Feeds produced by the Internet Research Agency, the Kremlin’s official troll army. Perhaps more than 140 million — on Facebook and Instagram combined — might have been served a story produced by dubious Russian sources as a result of their friends interacting with that content. And about 10 million users saw ads purchased by Kremlin agents around Election Day.

Not all of those affected users, however, can take advantage of Facebook’s forthcoming transparency tool.

The new disclosure portal only aids those who directly followed one of the accounts or pages set up by Russian forces on Instagram and Facebook — not users who may have seen Kremlin-sponsored content because their friends “Liked” it and it subsequently appeared in their News Feeds. Nor does Facebook’s new effort help those who may have viewed any of the roughly 3,000 election-timed ads purchased by Russia’s so-called IRA.

In the end, Facebook declined to say Wednesday exactly how many users could actually take advantage of its new transparency hub, though it is likely in the millions. Previously, though, companies’ leaders have expressed doubts that they even have the ability to reach out to 140 million or more Americans that might have viewed Kremlin propaganda.

“It's a much more challenging issue to identify and notify reliably people who may have been exposed to this content on an individual basis,” said Colin Stretch, the company’s general counsel, during an appearance on Capitol Hill last month.

Stretch’s comments at the time — and Facebook’s announcement today — respond to lawmakers who have urged Facebook to proactively inform users who may have been affected by Russia’s disinformation campaign. That list includes Sen. Richard Blumenthal, a Democrat, who wrote Facebook and its peers a letter in November stressing they had to tell their users if they “may have been unwitting participants” in the Kremlin’s efforts.

All three tech giants had until today to inform Blumenthal of their plans. Spokespeople for Google and Twitter did not immediately respond to emails seeking comment on Wednesday.

On Google, Russian actors purchased a small number of ads around the 2016 presidential election. On Twitter, Russian trolls maintained thousands of since-shuttered accounts, often amplified by bots. And like Facebook, both Google and Twitter have promised to harden their platforms against disinformation entering the next U.S. election in 2018 while introducing new political ad transparency measures.

“It is important that people understand how foreign actors tried to sow division and mistrust using Facebook before and after the 2016 U.S. election,” Facebook said in its blog post revealing its new transparency project.

“That's why as we have discovered information, we have continually come forward to share it publicly, and have provided it to congressional investigators. And it's also why we're building the tool we are announcing today,” the company said.

Sign up for the newsletter Recode Daily Email (required) By signing up, you agree to our Privacy Notice and European users agree to the data transfer policy. Subscribe