On March 15 last year, 51 people were killed including dozens at Al Noor Mosque. Photo: Mark Mitchell / NZH
The man - who continues to have name suppression - was an 18-year-old when the livestream was shared of the March 15 shootings last year.
He pleaded guilty, by video link, to possession of objectionable material and also guilty to a later indecent act on a 12-year-old.
The man was remanded in custody.
He will reappear in court for sentencing on November 26.
Judge John Brandts-Giesen says name suppression will continue until his appearance in person in court.
The judge told the man he was now subject to the three strike law.
The shooter, who pleaded guilty to killing 51 people in the Christchurch mosque terrorist attack, is scheduled to be sentenced starting August 24.
