AFCP stands for AXS File Concatenation Protocol, and is a poorly designed protocol for appending information to the end of files. This can be used as an auxiliary technique to store IPTC information in images, but is incompatible with some file formats.
ExifTool will read and write (but not create) AFCP IPTC information in JPEG images, but not other image formats.
Tag ID Tag Name Writable Values / Notes 'IPTC' IPTC - --> IPTC Tags 'Nail' ThumbnailImage N 'PrVw' PreviewImage N 'TEXT' Text N