The coroner investigating the death of Molly Russell is writing to social media companies demanding they hand over information from her accounts.
Molly was 14 when she ended her own life in 2017 after viewing graphic content about suicide and self harm.
At a pre-inquest hearing, coroner Andrew Walker said he would be writing to Instagram, Snapchat and Whatsapp demanding they share the material.
It is thought to be the first time a coroner has made such an order.
Molly's family, from Harrow, north-west London, believe some of the blame for her death lies with the companies.
Family barrister Jess Elliott told the court the platforms provided access to "a self-supplying world of self harm and suicide" which "normalised" such behaviour.
Mr Walker said the inquest needed to find out whether the "accumulated effect" of the material "overwhelmed" the teenager.
Pinterest, which Molly also used, was present at the hearing and said it was "extremely keen to do everything it can to assist".
Separately, the family said it was "surprising" and "disappointed", that police officers investigating Molly's devices had not attended.
At a previous hearing officers said they had accessed both an iPhone and iPod Touch obtaining the equivalent of tens of thousands of pages of data.
After initially saying that material could be handed to the family the Met has now indicated it is unable to do so because of a legal problem.
Last month Instagram pledged to remove images, drawings and even cartoons showing methods of self-harm or suicide.
It extended measures announced in February, which banned "graphic images of self-harm" and restricted those with suicidal themes.
Instagram has been under pressure to act after Mr Russell said he believed the US-based service had been partly responsible for his daughter's death.
After she died, Mr Russell found graphic material about self-harm and suicide on her Instagram and Pinterest accounts.
A date for the start of the full inquest has not yet been set.