The watchdog behind the initiative says there has been a huge rise in the number of pictures and videos available on the internet.
A web page showing a child being sexually abused is identified every eight minutes – with some victims younger than two years old.
The figure has come from the Internet Watch Foundation (IWF), which is marking its 20th anniversary with the global release of a “hash list” to stop child sex abuse images being shared online.
Since it was formed on 21 October, 1996 the watchdog says it has identified and removed more than a quarter of a million URLs.
As well as removing web pages, the IWF has also logged 125,000 “digital fingerprints”, known as “hashes”, which are a unique code generated from the data in an image.
Experts have compiled a database of individual codes of known images of child sexual abuse to tackle the issue of duplicated material.
It is asking internet companies around the world to use the system – developed with Microsoft – to stop the upload, sharing and storage of abuse images.
IWF chief executive Susie Hargreaves described the hash list as a “major breakthrough”.
She said: “Every eight minutes our analysts identify a new web page showing a child being sexually abused.
“We always ensure that image is taken down, but in the past it could be uploaded again and again.
“Now our new technology allows us, and any company which uses the image hash list, to hunt out those abusive images… completely stamp out copies and even stop the image being uploaded in the first place.”
The parents of murdered April Jones are among those who have voiced their support for the IWF’s work.
The five-year-old’s killer, Mark Bridger, was found to have accessed child abuse images online before her death.
April’s father, Paul Jones, said: “The more of this you can remove, take away, it’s going to be the better so potential paedophiles haven’t got the chance to see these images and then move on to the next stage.”