The offences included 136 counts of rape and 110 counts of sexual intercourse with a child under 10 allegedly committed in Brisbane, Sydney and overseas between 2007 and 2022.
Police on Tuesday moved to reassure parents they had contacted the families of all the children who appeared in the thousands of images of alleged child abuse material.
The major investigation dates back to 2014, when an officer in Queensland found images and videos of child abuse on the dark web and uploaded them to an international victim identification database.
No matches came through until 2022, when the Australian Federal Police traced objects identified in the background of images posted between 2013 and 2014 to a Brisbane childcare centre.
Police contacted the centre and the alleged offender's identity was revealed, leading to his arrest on August 21 last year in Brisbane.
The 45-year-old was initially charged with two counts of making child exploitation material and one count of using a carriage service for child pornography material.
Police launched a joint operation, involving AFP and Queensland officers, after the arrest.
AFP Assistant Commissioner Justine Gough said within 48 hours police had executed search warrants, including at the man's Gold Coast home, and seized electronic devices allegedly containing child abuse material.
Investigators trawled through about 4000 images and videos the man had allegedly created.
Ms Gough said the process of identifying the children in the material took time, skill and determination and she thanked officers for working for years to uncover the identities of the man and his alleged victims.
Police say the offences took place at 10 childcare centres in Brisbane between 2007 and 2013, and 2018 and 2022, an overseas location in 2013 and 2014, and at a centre in Sydney between 2014 and 2017.
A total of 1623 charges have been laid against the man.
Ms Gough said all parents of the 87 prepubescent Australian girls identified from the material had been notified, with some of the alleged child abuse victims now aged over 18.
"Can I please underscore that message to parents and carers, all of the parents and carers of Australian children who were recorded in the alleged child abuse material have been identified as part of the investigation," she said.
The AFP is working with international police to identify four alleged victims overseas.
The man was qualified to work with children and had never been the subject of complaints by parents.
NSW Police Assistant Commissioner Michael Fitzgerald said officers from his state would seek the man's extradition to face a further 180 charges of child sexual abuse.
He said the charges, if proven, carried a term of life imprisonment.
"This is one of the most horrific child abuse cases that I've seen in nearly 40 years of policing in NSW,'' Mr Fitzgerald said.
"Police will continue to relentlessly pursue this matter; on behalf of the 23 victims, it will remain our number-one priority.
"I can only say, you try not to be shocked after a long period of time in the police and crime reporting but this is a horrific case."
Queensland acting Assistant Commissioner Col Briggs said it was an incredibly difficult and long investigation between a number of jurisdictions.
The case is scheduled for mention in Brisbane Magistrates Court on August 21.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
Lifeline 13 11 14
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
