Stephen George Garside’s collection of videos and pictures included some featuring children as young as two, said Brooke Morrison, prosecuting.
He had printed off some of the images off and made a photo album of them.
Garside had been downloading sexual images of children for 12 years by the time police put a stop to his crimes.
Officers arrested him at his place of work and searched his work locker and his home near Malton.
After pleading guilty to a series of online sex charges, Garside claimed to a probation officer that he was interested in adult pornography and never looked for sexual images of children online, York Crown Court heard.
But deputy circuit judge Deborah Sherwin dismissed that claim.
“It is clear to me you have held an interest in child pornography for many years,” she said. “This was sexually motivated by the need to satisfy your needs, you not having experienced a sexual relationship in your adult life.”
She jailed Garside for 18 months. She also put him on the sex offenders’ register for 10 years and made him subject to a sexual harm prevention order (SHPO) indefinitely.
The order will restrict his use of the internet and enable police to monitor what he does online.
Garside, 58, of Saxon Drive, Rillington, near Malton, pleaded guilty to six charges of making indecent images of children by downloading them, one of distributing a small number of images from the least serious category, one of having extreme pornography and one of having prohibited images of children.
He represented himself and when asked by the judge if he wanted to give any mitigation, declined.
Ms Morrison said police went to Garside’s home and place of work on July 7, 2020. They found him at work and searched him. They also searched his work locker and his home and seized a number of internet devices and related items.
Forensic checks revealed that between them, the seized devices and items contained 333,337 videos and pictures, all but 115 of them were of children. There were 373 videos of which all but one were of children. There were 94 sexual videos of children of the most serious category, 51 of the middle category and 219 of the least serious category. There were seven prohibited videos of children and one sexually extreme video.
There were 321 sexual pictures of children of the most serious category, 606 of the middle category and 332,237 of the least serious category, 114 sexually extreme pictures and 59 prohibited pictures of children.
The earliest material was dated 2008 and dates on other material showed he had continued to download material up until his arrest 12 years later.
On two occasions, he had used “torrent” software to distribute a very small number of the images of the least category online.