A senior executive at social media site Pinterest has said he is "sorry" for content viewed by a 14-year-old who took her own life after viewing it.
Judson Hoffman admitted at an inquest that when Molly Russell was viewing the content on the platform in 2017, the site was not safe.
Molly, from Harrow, north-west London, died in November 2017.
Her father, Ian, earlier told North London Coroner's Court that social media was instrumental in her death.
Mr Hoffman, Pinterest's global head of community operations, said he was "not able to answer" how children could agree to potentially being exposed to content inappropriate for a child.
In the platform's terms of service, displayed to the court, users were asked to report "bad stuff" if they saw it on the site. The terms of service, from November 2016, said users might be exposed to material that was "inappropriate to children".
The Russell family's barrister, Oliver Sanders KC, asked: "Bearing in mind it might be children who are opening the account… when a user opens an account they have to agree there may be content that's inappropriate for a child. If the user is a child, how can they agree to that?"
"I'm sorry, I'm not able to answer that," Mr Hoffman said.
Mr Hoffman said he deeply regretted that Molly saw content relating to self-harm, suicide and depression on the platform.
He was taken through a number of images the company had sent to Molly via email before her death, with headings such as "10 depression pins you might like" and "depression recovery, depressed girl and more pins trending on Pinterest".
The emails also contained images about which Mr Sanders asked Mr Hoffman if he believed they were "safe for children to see".
Mr Hoffman replied: "So, I want to be careful here because of the guidance that we have seen.
"I will say that this is the type of content that we wouldn't like anyone spending a lot of time with."
Mr Sanders said "particularly children" would find it "very difficult… to make sense" of the content, to which Mr Hoffman replied: "Yes."
The court heard how Pinterest used artificial intelligence and human moderators to hide or remove content related to self-harm and suicide, a system that was "largely successful" but users might still encounter such content.
Family barrister Mr Sanders suggested to Mr Hoffman the platform had "chosen to take a risk" when there was a "no-risk option" of not allowing children on Pinterest.
Mr Hoffman replied: "I would say 'chosen an option other than absolutely no risk', I would not say 'risky option'… obviously our intention is to reduce the risk."
The hearing was shown two streams of content Molly had seen on Pinterest, comparing the material she viewed earlier in her use of the platform and in the months closer to her death.
While the earlier stream of content included a wide variety of content, the latter focused on depression, self-harm and suicide.
Asked by Mr Sanders if he agreed that the type of content had changed, Mr Hoffman said: "I do and it's important to note, and I deeply regret that she was able to access some of the content shown."
Mr Hoffman agreed the platform was not safe when Molly used it - and admits harmful content still "likely exists" on the site.
Mr Sanders asked: "Pinterest accepts that its platform should be safe for children?"
Mr Hoffman replied: "It should be safe for everyone on the platform."
Mr Sanders continued: "And it accepts that in 2017, when Molly was on it, it wasn't safe?"
Mr Hoffman replied: "That's correct, there was content that should have been removed that was not removed.
"Content that violates our policies still likely exists on our platform. It's safe but imperfect and we strive every day to make it safer and safer."
Coroner Andrew Walker asked: "It's not as safe as it could be?"
Mr Hoffman replied: "Yes, because it could be perfect."
Earlier in the day, the inquest also heard how Molly tried to ask for help from celebrities.
Molly's father, Ian Russell, said his daughter had reached out for help on Twitter to personalities with thousands or even millions of followers, who would not even necessarily notice a tweet from someone like Molly.
He added: "She was calling out to an empty void."
One message, sent to US actress Lili Reinhart, which was read to the court, said: "I can't take it any more. I need to reach out to someone, I just can't take it."
Mr Russell, who previously told the inquest he was shocked that "dark, graphic, harmful material" was readily available to be seen by children online, questioned how Molly knew "how to get into this state" and he "found it hard to believe that some of the most powerful global brands in the world" could not find a way to help prevent such content reaching vulnerable people.