# Apple Partition Map - ISO 9660 - UDF Hybrid Disk Image

> disc image format

**Wikidata**: [Q114075181](https://www.wikidata.org/wiki/Q114075181)  
**Source**: https://4ort.xyz/entity/apple-partition-map-iso-9660-udf-hybrid-disk-image

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## Summary  
The **Apple Partition Map - ISO 9660 - UDF Hybrid Disk Image** is a disk image format that combines multiple partitioning and file system standards into a single file. It is based on the Apple Partition Map scheme and supports ISO 9660 and UDF file systems, making it versatile for cross-platform data storage and distribution. This format is commonly used for software distribution and archival purposes.

## Key Facts  
- **Instance of**: Disk image (a computer file containing the contents and structure of a disk volume)  
- **Based on**: Apple Partition Map (a disk partitioning scheme)  
- **File extensions**: `.iso`, `.toast`, `.dmg`  
- **PRONOM file format ID**: `fmt/1757` (as registered by the National Archives UK)  
- **Primary use**: Combines ISO 9660 (common for CDs/DVDs) and UDF (universal disk format) for broader compatibility  

## FAQs  
### Q: What file extensions are associated with this disk image format?  
A: The format uses `.iso`, `.toast`, and `.dmg` extensions, with `.iso` being the most widely recognized for cross-platform compatibility.  

### Q: What is the purpose of combining multiple standards in this format?  
A: By integrating Apple Partition Map, ISO 9660, and UDF, the format ensures compatibility across macOS, Windows, and other systems, making it ideal for software distribution.  

### Q: Where is this format officially documented?  
A: It is registered in the PRONOM database (ID: `fmt/1757`) maintained by the UK National Archives, which catalogs file formats for digital preservation.  

## Why It Matters  
This hybrid disk image format addresses the challenge of cross-platform data sharing by unifying Apple Partition Map (used in macOS environments) with ISO 9660 and UDF (widely supported for optical media). Its versatility makes it a preferred choice for software installers, archival backups, and legacy system support. By bridging macOS and broader industry standards, it simplifies distribution and ensures accessibility across operating systems without requiring proprietary tools.  

## Notable For  
- **Hybrid compatibility**: Seamlessly merges Apple Partition Map with ISO 9660/UDF, rare for disk image formats.  
- **Multi-extension support**: Recognized by `.iso`, `.toast`, and `.dmg`, catering to diverse use cases.  
- **PRONOM registration**: Officially documented as a preserved file format (`fmt/1757`), underscoring its archival relevance.  

## Body  
### Technical Basis  
- Built on **Apple Partition Map**, a partitioning scheme historically used for Macintosh disks.  
- Incorporates **ISO 9660** (standard for CD/DVD file systems) and **UDF** (Universal Disk Format) for broader interoperability.  

### File Extensions  
- `.iso`: Generic extension for ISO 9660-compliant images.  
- `.toast`: Associated with Roxio Toast software, often used for burning disk images.  
- `.dmg`: Native Apple Disk Image format, sometimes used interchangeably.  

### Preservation Status  
- Listed in the **PRONOM database** (`fmt/1757`), a trusted resource for digital preservation metadata.  

### Use Cases  
- **Software distribution**: Ensures installers work across macOS and other OSes.  
- **Archival**: Combines robustness of Apple Partition Map with universal readability of ISO/UDF.  

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## References

1. [Source](https://www.nationalarchives.gov.uk/PRONOM/fmt/1757)