Jack Coulson, 19, was found guilty last year of constructing the explosive device but avoided jail when he was given a youth rehabilitation order.
-> Huge fire battled by 100 firefighters in Leeds is being treated as arsonOn Monday, in a separate prosecution, Coulson admitted an offence of possessing a document or record for terrorist purposes when he appeared at Leeds Crown Court.
Judge Geoffrey Marson QC heard Coulson, of Mexborough, South Yorkshire, admit that between between January 3 and January 20 this year, he possessed a document called The Big Book Of Mischief.
The court heard the document contained information of a kind likely to be useful to a person looking to commit an act of terrorism.
Coulson, who appeared in court wearing black trousers and an open-necked, short-sleeved, pale blue shirt, was remanded in custody by Judge Marson.
He will be sentenced on Thursday.
Coulson was not named in reports of his previous trial, in early 2017, after the court banned his identification because he was 17 years old at the time.
That jury heard how the pipe bomb was found in a desk drawer in his Bradford bedroom after police were alerted through suspicious Snapchat messages.
-> Motorcyclist critical after crash in LeedsProsecutors said one of these messages was a cartoon-like image of a mosque being blown along with words describing 'retribution'.
Another was a picture of a pipe bomb with an image of the Bradford skyline and the message: "Incendiary explosive and home-made black powder.
The jury heard how officers found the defendant's bedroom covered in flags, including the swastika and the symbol of the Waffen SS as well as a laptop with wallpaper featuring a Nazi eagle over a swastika and the German phrase: One Nation, One Empire, One Leader.
But the teenager told the court he never intended to use the pipe bomb.
The judge in the trial, Mr Justice Goss, said that the defendant's "perverted" views led to him celebrating the murder of Labour MP Jo Cox and proclaiming her murderer, Thomas Mair, as a hero.
-> Storm Chris: When will the ex-hurricane hit the UK and what will Yorkshire's weather be like?Sentencing Coulson in February 2017, the judge said: "You are quite unable to articulate why you are now sorry and you continue to express very extreme views."
He said Coulson was associated with National Action, which is now a proscribed terror group and was described in court as "a small, secretive neo-Nazi British youth nationalist organisation".
Coulson was found guilty by the jury of constructing the explosive device but not guilty of a terrorism offence.
He was given a youth rehabilitation order to last for three years which would involve him being supervised, attending a preventative intervention programme for a year, staying off the internet and not contacting any proscribed groups.