IWF Hash list

What is the IWF Hash list?

We have a growing list of hashes of child sexual abuse imagery. A hash is a unique code – like a digital fingerprint of an image. Using PhotoDNA and MD5 technology, we create hashes of the child sexual abuse content we see and we add these to our Hash List.

Why is this Hash List important?

Three trained IWF experts have looked at each image and assessed it before a hashed image is included on the list. We use these hashes to help us find duplicate images of child sexual abuse. This makes us more efficient at what we do. Up to 99 pieces of data are recorded against each image. This helps us to build a growing picture of the nature of child sexual abuse imagery on the open internet.

How does this help technology companies?

When technology companies use our Hash List, it helps them to stop the sharing, storage and even the upload of child sexual abuse content. To make it easy for technology companies to use, each hashed image is graded according to international standards so companies have confidence in the data we provide them.

  • At the end of 2020, the list contained hashes relating to 567,176 individual images.
  • Of these hashes, 118,074 (21%) related to the worst form of abuse – images of rape or sexual torture of children.

During 2020, we’ve increased the size of the Hash List by 95,937 hashes. This means that in 2020, our analysts assessed and hashed 8,722 images each, alongside assessing public reports, and actively searching for child sexual abuse images and videos.