In order to create custom audience within Advertising Audience the data that you upload must be formatted correctly.
Customer Match data files must follow correct formatting guidelines for uploading hashed data. Incorrect formatting, including incorrect hashing, can lead to an upload error or a low number of matched records.For example: +12345678910, +811234567891, +0212345678 NOT 0212345678, 811234567891, 12345678910
Further information can be found here. This includes formatting guidelines for other attributes such as Email, First Name, Last Name etc
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