(registered 2026-04-07, last updated 2026-04-07) Type name: application Subtype name: vnd.phbk+xml Required parameters: charset (Encoding: UTF-8) Optional parameters: N/A Encoding considerations: 8bit Since this is a text-based XML format, 8bit encoding is sufficient for transporting contact data like names and addresses. Security considerations: The .phbk format is a non-executable, text-based XML structure used for storing contact information such as phone numbers, emails, and physical addresses. It does not contain active content, scripts, or macros. There is no risk of code execution on the host machine. Implementers should follow the security considerations outlined in RFC 7303, Section 10 (https://www.rfc-editor.org/rfc/rfc7303#section-10), particularly regarding external entity expansion and recursive processing. Interoperability considerations: This format is designed to be parsed by any XML-compliant software. It has been tested on mobile platforms (Android) and desktop systems to ensure consistent data rendering. Published specification: https://github.com/afifashamsadvivo/phbk Applications that use this media type: Custom phonebook managers and contact backup utilities. Fragment Identifier Considerations: The .phbk file type does not use or require fragment identifiers. It is intended for custom configurations and data storage in AI-based systems, not for referencing specific document fragments. Restrictions on Usage: The .phbk file type is primarily intended for use in technical environments related to AI projects. It is not designed for general public use or non-technical applications. Additional information: Deprecated Alias Names: There are no deprecated alias names for the .phbk file type. Magic number(s): None. Identification is based on the .phbk file extension or the root element. File extension(s): .phbk Macintosh file type code(s): TEXT Person & email address to contact for further information: afifashamsadvivo - afifashamsad.vivo&gmail.com Intended usage: COMMON Author/Change controller: Lost Idea Experiments (afifashamsad.vivo&gmail.com)