On Instagram, a detail from a medieval painting was superimposed with words suggesting Jews were responsible for the deaths of children.

On Twitter, a photoshopped image of world leaders with the Star of David on their foreheads was posted above the hashtag #JewWorldOrder.

On YouTube, a video of the World Trade Center on fire was used as a backdrop for an argument that Jews were responsible for the 2001 terrorist attacks on the towers.

All are examples of anti-Semitic content explicitly banned by social media companies. They were shared on social media and allowed to remain up even after they were reported to social media companies, according to a report released on Friday by the Center for Countering Digital Hate, a nonprofit organization.

The study, which found that social media companies acted on fewer than one in six reported examples of anti-Semitism, comes alongside a report with similar findings from the Anti-Defamation League. Both organizations found that anti-Semitic content was being widely shared on major social media platforms and that the companies were failing to take it down — even after it was reported to them.

"As a result of their failure to enforce their own rules, social media platforms like Facebook have become safe places to spread racism and propaganda against Jews," the Center for Countering Digital Hate said.

Using tools the platforms created for users to report posts with hate speech, nudity and other banned content, the center's researchers spent six weeks reporting hundreds of anti-Semitic posts to Facebook, Instagram, Twitter, YouTube and TikTok. In all, the posts they analyzed were seen by up to 7.3 million people.

They found that Facebook and Twitter had the poorest rates of enforcement action. Of the posts reported to them as anti-Semitic, Facebook acted on roughly 10.9 percent. Twitter, the report said, acted on 11 percent. YouTube, by comparison, acted on 21 percent and TikTok on 18.5 percent.

There were millions of views of the anti-Semitic content on both YouTube and TikTok. On Twitter and Facebook, the views were in the hundreds of thousands.

"While we have made progress in fighting anti-Semitism on Facebook, our work is never done," said Dani Lever, a Facebook spokeswoman. She added that the prevalence of hate speech on Facebook was decreasing.

"Given the alarming rise in anti-Semitism around the world, we have and will continue to take significant action through our policies," Lever said.

A Twitter spokesperson said the company condemned anti-Semitism and was working to make Twitter a safer place for online engagement.

TikTok said in a statement that it proactively removes accounts and content that violate its policies, and that it condemns anti-Semitism and does not tolerate hate speech.

YouTube said in a statement that it had "made significant progress" in removing hate speech over the last few years.

The Anti-Defamation League's survey was similar but smaller. It reported between three and 11 pieces of content on each of the same platforms, as well as on Reddit, Twitch and the gaming platform Roblox. It gave each platform a grade, such as a C- for Facebook and TikTok and a D for Roblox, based on how quickly the companies responded and removed the posts. The highest-rated platform, Twitter, received a B-.

"We were frustrated but unsurprised to see mediocre grades across the board," said Jonathan Greenblatt, the chief executive of the organization.