The 17-year-old from Bradford told Leeds Crown Court he hoped people would think he wanted to blow up a mosque.
He also he said he posted offensive comments online "to get a reaction".
He denies the preparation of terrorist acts and an alternative count of making explosives.
The boy, who cannot be named because of his age, was arrested by counter-terrorism police after a member of the public reported a series of Snapchat messages sent by the defendant, including an image of a "viable" home-made pipe bomb.
The jury has previously heard he posted a message saying "incendiary explosive and home-made black powder, more to come" over a photo of the device, and an emoji of a figure in a turban with a gun pointing to his head and an image of Bradford.
The defendant said he had built the bomb using plastic casing and sparklers months before posting the images.
He told jurors he had considered letting it off near a canal but had eventually left it in his bedroom desk.
Asked what the point was of making something he did not use, he replied: "Not sure. I don't really know. It was kind of a pointless thing to do."
Regarding the Snapchat images of the device, defence counsel Rupert Bowers asked: "Are you wanting this to look like a threat?"
The defendant said "yes" before later adding: "It wasn't a threat in that I wasn't actually going to carry through."
Mr Bowers asked what he wanted people to think.
"Christ he's planning at attack - he's going to do something," the boy answered.
The boy was also asked about his membership of neo-Nazi youth group National Action and his national socialist views.
Asked if he still held those views, he said: "Yes."
He told the court he become a national socialist "about a year ago" before joining National Action.
The defendant admitted wearing a Nazi uniform during online video conversations and said he did so in order to "offend people".
"I find it easier to shock people than have a proper conversation," he told the court
The trial continues.
A teenage boy who posted images of a home-made pipe bomb online said he wanted people to think he was "planning an attack" but had no intention of carrying one out, a court has heard.