Commons:International Standard Content Code
International Standard Content Code (ISCC) is a perceptual hash of a media file which makes it possible to recognize an image even though it has been saved in another format, scaled, or distorted in other ways. Wikidata property ISCC code (P13150) on Wikidata allows the value to be stored as structured data. Note that an edit to a file will change the hash slightly, so it's best to qualify the value with the Wikimedia page-version URL (P7569). See more metadata modeling for structured data.
ISCC was first created as an open standard which can be found at iscc.codes. Later it was also accepted as ISO 24138:2024.
File types
ISCC can be created for a number of different file types (list in the SDK). Below is a list with all the file types found in Special:MediaStatistics and what has been tried so far. Those marked 
Not OK are not supported by the standard.
Tools
CommonsDB registry explorer
The CommonsDB project has a registry where files or ISCC codes can be compared to what is in there. As of June 2026, it has images from both Wikimedia Commons and Europeana.
User scripts
The user script isccUpload.js generates an ISCC of an image during the upload process which can be copied and later added as structured data.
The user script commonsdb-link.js adds a link underneath the ISCC value in structured data to the CommonsDB registry explorer so that a user can see if it exists there.
Template
Template:ISCC can be used on a file page to create a link to the CommonsDB registry explorer (and other tools can also be added). See the template documentation for more features.
Active bot work
AinaliBot is currently adding ISCC codes as structured data. All images the bot adds this to has also been declared in the CommonsDB registry.
Potential usefulness for Wikimedia Commons
Besides being able to find similar images in the CommonsDB registry as shown above, it can also be useful on Wikimedia Commons in various ways. The video shows a prototype on how the upload process could be supported. There are also possibilities to check for similar images already on Commons, see this overview page on Meta.