If one wanted to upload their customer list into Facebook's Custom Audience tool, could one pre-hash the data before loading it into the browser upload tool?

I know that the data is hashed before being uploaded to Facebook. But what if one needed to give the list to an agency that would be uploading the list for them? In order to maintain security the controller of the data would want to hash the information before handing it over to an agency.

2 Answers 2


I've contacted Facebook support in regard to this issue and they have confirmed that you cannot upload pre-hashed data. It's mandatory for the data to be un-hashed.

  • Thanks @Cosmin Sipos
    – gillytech
    Oct 17, 2020 at 19:21

You can, at least as of year 2021. Need to use particular flavor of sha-256 though. I just did that, and it got accepted.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.