Ashley Paul Griffith, 46, confessed to committing 307 offences at childcare centres in Brisbane and Italy between 2003 and 2022, a Queensland court heard on Monday.
Most of Griffith's victims were under the age of 12, the court heard. The judge's associate took over two hours to read out all of the charges against him.
Police have previously described Griffith as one of Australia's worst-ever paedophiles.
The charges against him included 28 counts of rape, 190 counts of indecent treatment, 67 counts of making child exploitation material, four counts of producing such material, and one count of distributing it.
Several of his victims and their families were in court on Monday, and some parents cried when the names of their children were read out, according to ABC News.
"We see people going [into the childcare centre now] and I think, this happened to my child in that room," said one child's mother. "It’s a room of horrors."
The same child's father said he could not believe how Griffith could have gotten away with his crimes for 20 years.
"As she grows up, we'll deal with that as it comes but it’s going to be something we deal with through our lives now," her father said.
Griffith was arrested in August 2022 by Australia's federal police, after they found thousands of photographs and videos related to his abuse that were uploaded onto the dark web.
Although faces were cropped out of the footage, investigators managed to trace them to Griffith because of a unique set of bedsheets seen in the background of the videos.
Police believe he recorded all his offences on his phones and cameras.
He was charged in November last year with more than 1,600 child sex offences, but most of these were eventually dropped.
Griffith remains in custody and will be sentenced at a later date.The 45-year-old man has been in custody in Queensland since August 2022 when he was initially charged with two counts of making child exploitation material and one count of using a carriage service (electronic communication) for child pornography material.
Griffith has been charged with 110 counts of sexual intercourse with a child under 10.
Additional self-produced child abuse material was discovered on electronic devices allegedly owned by the accused, leading to additional charges against him, per the Daily Mail.
"Operation Tenterfield," which was launched immediately after the man's arrest, has focused on identifying the children featured in the alleged child abuse material.
The investigation revealed that the man recorded his offences on phones and cameras while working at 10 childcare centers in Brisbane between 2007 and 2013, and again from 2018 to 2022.
