What is the XMB file format?
.xmb files are binary-compiled XML data files used by Ensemble Studios game titles including Age of Mythology (2002), Age of Empires III (2005), and Halo 3 (Xbox 360, 2007). Rather than shipping raw XML files that must be parsed at runtime, the Ensemble Studios engine pre-compiles XML game data - scenario configurations, unit definitions, string tables, and AI scripts - into a compact binary tree format that loads faster at game startup.
The format stores XML element names, attributes, and values in a flattened binary structure using little-endian byte order. Files frequently appear with a double extension such as proto.xml.xmb or strings.xml.xmb, signaling that the .xmb is the binary form of a corresponding .xml source. Some variants are GZIP-compressed. There is no public magic byte specification; files are identified by game context.
Modders work with .xmb files by converting them to plain .xml using community tools such as AoM XMB Converter or the Corsair AoE3 Modding Tool, making edits in a text editor, then recompiling. A notable naming conflict: Sony's PlayStation 3 XrossMediaBar (XMB) UI also uses an XML-based format called XMBML - this is entirely unrelated to the Ensemble Studios format.
The format has no known successor in Ensemble's lineage; the studio was closed by Microsoft in 2009, though the Age of Empires franchise continues under Relic Entertainment and World's Edge.
Security & safety
RISK: LOWGame data files; not executable. No known malware vector.
Format details
in a nutshell- PS3 XMBML Interface File - Sony PlayStation 3 uses XMB-extension files for the XrossMediaBar UI shell; unrelated binary format.
- LucasArts X-Wing Mission Briefing - Historical LucasArts game files also used .xmb; rare and legacy.
Programs that open XMB files
Windows2 apps
AoM XMB Converter (community tool)
Free Drop the .xmb onto the converter to get an editable .xml, then open the .xml in any text editor.
Corsair AoE3 Modding Tool
Free Use to convert XMB ↔ XML for Age of Mythology and Age of Empires III files. Technical details
deep spec| File type | Binary-compiled XML game data - pre-parsed binary tree replacing runtime XML parsing |
| Byte order | Little-endian |
| Container | Proprietary Ensemble Studios binary-XML container |
| Compression | None or GZIP (variant-dependent; some game builds ship compressed .xmb files) |
| Typical file size | 1 KB - 500 KB |
| File naming convention | Often double-extension: e.g., proto.xml.xmb or strings.xml.xmb - signals the .xmb is the compiled form of a .xml source |
| Internal structure | Binary tree encoding element names, attribute names/values, and text nodes for fast game-engine loading |
| Known game titles | Age of Mythology (2002), Age of Empires III (2005), Halo 3 (Xbox 360, 2007) |
| Format variants | Structure differs across Age of Mythology, Age of Empires III, and Halo 3 builds |
| Modding workflow | XMB → XML decompile with AoM XMB Converter or Corsair; edit XML; recompile to XMB |
| Naming conflict | Sony PlayStation 3 XrossMediaBar UI uses an unrelated XML format called XMBML - entirely different from this format |
| Developer studio | Ensemble Studios (Microsoft); studio closed 2009; Age of Empires franchise continued by Relic Entertainment and World's Edge |
| Released | c. 2002 (Age of Mythology) |
XMB conversions
Community Q&A
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