Daniel Harris, 19, posted videos which were shared by Payton Gendron, who has admitted a supermarket shooting in Buffalo, New York, and linked to Anderson Lee Aldrich, the only suspect in a shooting at a gay bar in Colorado, Manchester Crown Court heard.
Sentencing Harris, Judge Patrick Field KC said: “What they did was truly appalling but what they did was no more than you intended to encourage others to do when publishing this material online.”
Referring to Gendron, 19, who has pleaded guilty to murder and hate-motivated terrorism charges, the judge said: “This indicates that at the very least the material you produced and published has had some influence upon the young man, and I note he was a similar age to you, who went out and shot 10 black people dead in a store in Buffalo.”
He said he had “no hesitation” in coming to the conclusion that Harris, from Derbyshire, was “highly dangerous” and passed an extended sentence, with a licence period of three years on top of the custodial sentence.
The teenager, who wore a grey suit, was found guilty following a trial of five counts of encouraging terrorism and one count of possession of material for terrorist purposes, relating to a 3D printer he was trying to use to make firearm parts.
The court heard his offences were carried out over a period of 14 months and began when Harris was 17.
Judge Field said: “You were, throughout that time, a propagandist for an extremist right-wing ideology. You were in close touch with other right-wing extremists online and there can be little doubt that you shared ideas between you.”
The court heard the videos he produced glorified mass murderers and encouraged others to emulate them by carrying out similar attacks.
One video, called How to Achieve Victory, said there was a need for “total extermination of sub-humans once and for all”, the court was told.
Judge Field said Harris had previous convictions including the racially aggravated criminal damage of a memorial to George Floyd in Manchester.
He was engaged with a deradicalisation programme, but told the operative his behaviour was a “blip” and denied having any interest in politics.
At the time he made those claims, the court heard, he was creating a video homage to Thomas Mair, who murdered MP Jo Cox.
The judge said he demonstrated “a level of deceit and cunning”.
Joe Allman, prosecuting, said investigations following the shooting in which five people died at Club Q in Colorado revealed a link between videos posted by Harris and the only suspect in the attack, Anderson Lee Aldrich.
Mr Allman added: “The Crown say it demonstrates that individuals of the greatest concern have accessed the material produced by Mr Harris.”
James Walker, defending, said Harris, of Lord Street, Glossop, was withdrawn from mainstream school at the age of seven and there had been “quite disgraceful failings” by his family and the local authority.