Hashing is a type of cryptographic security method which turns the information in your customer list into randomized code. The process cannot be reversed.
For customer lists, automatic advanced matching and the Conversions API, some customer information is hashed before it’s sent to Meta technologies. Meta uses this hashed information and compares it to our own hashed information to build custom audiences or more accurately determine which people took action in response to your ad.
The hashed customer information, whether matched or not, is deleted promptly after the match process is complete.