By Emily Glazer and Sam Schechner

The 2020 election spurred social-media giants to adopt aggressive changes to how they police political discourse. Now the questions are whether that new approach will last and whether it should.

During the course of the contentious U.S. presidential campaign, and its messy denouement, Facebook Inc. and Twitter Inc. have taken steps that would have been unthinkable four years ago. They have applied fact-checking labels to posts from the U.S. president, deleted entire online communities and hobbled some functions of their own platforms to slow the spread of what they deemed false or dangerous content.

The companies -- in particular Twitter -- this month have been strict with warning labels on claims of voter fraud from President Trump and some of his supporters while Americans spent days awaiting vote-counting that was delayed by an unprecedented number of mail-in ballots.

For some lawmakers, mostly Democrats, the shift was overdue, while many Republicans accuse the tech firms of enforcing the rules inconsistently and allege the Silicon Valley giants are biased against conservatives.

Sen. Josh Hawley (R, Mo.), a Trump supporter who has been critical of social media, has tweeted about the moves and referred to them as the "#BigTech crackdown."

The companies have maintained they are committed to making sure users get reliable information about the election and not allowing falsehoods to spread. Taking on that role puts them in the uncomfortable position of having to make decisions about what they believe is true and what isn't.

The aggressiveness marks a shift for the social-media industry, which was paralyzed for years about whether to intervene on political speech, says Jenna Golden, former head of political and advocacy sales at Twitter.

"There was a bit of feeling frozen in what do we do, how do we do it and how do we do it fairly," said Ms. Golden, who now runs her own consulting firm. "I saw the thinking happening, but no one was ready to make any decisions."

A key turning point came in May, when Twitter for the first time placed a fact-checking advisory on one of Mr. Trump's tweets. By the time of the election, such notices were almost commonplace. On Saturday, the day media outlets called the race for now-President-elect Joe Biden, Mr. Trump tweeted six times -- Twitter labeled half of them as being disputed or misleading.

Mr. Trump has said Twitter is "out of control" and is censoring his views on the election.

Facebook also labeled Mr. Trump's posts, though it didn't hide them as did Twitter, which required users to click through labels to see the content. Facebook took other steps to intervene in how content spread, including dismantling a fast-growing group called "Stop the Steal," created by a pro-Trump organizations that were organizing protests of vote counts around the country. Facebook said it made the move because it "saw worrying calls for violence from some members of the group." The group's organizers said Facebook was selectively enforcing its rules to silence them.

The company later tightened its grip on speech across its platforms, including its Instagram photo-sharing app, invoking some of the emergency tools that executives previously described as their "break-glass" options to respond to possible postelection unrest.

Facebook spokesman Andy Stone said it has spent years preparing for safer, more secure elections. "There has never been a plan to make these temporary measures permanent and they will be rolled back just as they were rolled out -- with careful execution," he said, adding that temporary election protections were also used during the 2018 midterms and in other global elections.

While the severity of their measures varied, all the major social-media platforms took steps to label false election information or limit the spread of content they deemed dangerous. The popular short-video app TikTok, owned by ByteDance Ltd., banned all searches for "election fraud" last week.

YouTube says it has put an emphasis on elevating video-search results from authoritative sources and is also limiting recommendations to videos advancing baseless claims of voter fraud or premature calls of victory. A search Saturday on YouTube for an unfounded allegation that Democrats had used U.S. hacking software to alter election results -- something that Chris Krebs, director of the U.S. Cybersecurity and Infrastructure Security Agency described as "nonsense" -- returned several videos advancing the claim. By Sunday, results for that search had a banner saying, "The AP has called the Presidential race for Joe Biden."

A YouTube spokeswoman said it can take time for the company's system to trigger such banners. "We are exploring options to bring in external researchers to study our systems and learn more about our approach and we will continue to invest in more teams and new features," she added.

It is too early to quantify the effect of most of these moves, and researchers say the impact may never be fully known because not all of the interventions are disclosed. Still some of the efforts had noticeable results.

Take a tweet Mr. Trump sent on the evening before Election Day, contending a Supreme Court decision on voting in Pennsylvania would allow "unchecked cheating." In the nearly 37 minutes the tweet was available before Twitter labeled it as disputed and potentially misleading, it got 31,359 replies, retweets, quote tweets or retweets of quote tweets, according to Joe Bak-Coleman, a postdoctoral fellow at the University of Washington Center for an Informed Public. In the following 37 minutes, it brought in fewer than 5,700 -- a decline of 82%.

A separate analysis from social-media analytics firm Storyful found that Facebook posts by President Trump, his campaign and conservative outlets remained among the most viral on the platform in the days following the election. Storyful is owned by News Corp, which also owns Wall Street Journal publisher Dow Jones & Co.

The view that the rules are selectively enforced has led many conservatives to abandon Facebook and Twitter for other platforms, such as Parler. The app, which calls itself a "free speech social network," surged to the top of the download rankings for free apps this week.

In part because of that criticism, the larger platforms now face the challenge of articulating coherent enforcement strategies that can be applied consistently, including in other countries where the companies typically have fewer resources, say researchers who study social media and misinformation.

"Once a company makes a move once, it is much easier for them to do it again," said Graham Brookie, director of the Atlantic Council's DFRLab, which studies political misinformation. "We certainly crossed that Rubicon and aren't going back across."

Facebook has scheduled some postelection analysis sessions a few weeks after the election where employees are expected to discuss which measures that the company took in recent weeks should last longer, a person familiar with the matter said. Substantial changes would require Facebook CEO Mark Zuckerberg's approval, the person added.

One change that appears likely: Twitter said Mr. Trump's account, which has grown to more than 88 million followers, would no longer receive special privileges once he becomes a private citizen. The loss of those privileges, which are reserved for world leaders and public officials, would mean that some tweets that violate the site's rules would be taken down rather than labeled.

--Deepa Seetharaman contributed to this article.

Write to Emily Glazer at emily.glazer@wsj.com and Sam Schechner at sam.schechner@wsj.com

(END) Dow Jones Newswires

11-11-20 1133ET