What is the MB file format?
.mb files store 3D graphics data created by Maya software, developed by Autodesk. .mb is a binary file, in contrast to the similar .MA format, which stores data in plain text. Besides geometry, .mb files also contain data such as lighting settings, object textures, and animations. The format runs on Windows, macOS, and Linux.
Maya supports two types of scene persistence: ASCII (.ma format), where the whole project is saved in a text format, and binary (.mb format). The binary mode is the default save format. Binary files are smaller than ASCII text files and load faster, making them preferred in production pipelines. The underlying data remains the same regardless of the format used; .ma files also allow users to inspect and modify the file in a text editor.
Internally, .mb is built on an IFF-based chunked container. Files begin with FOR4 (32-bit) or, since Maya 2014, FOR8 (64-bit) to support scenes exceeding 2 GB. Related interchange formats include .FBX, .ABC, and .USD, though none replace .mb in a Maya-native pipeline.
Security & safety
RISK: LOWA .mb is scene data, not a program, so it can't run by itself. The realistic risk is via Maya scenes that embed scripts: Maya can store MEL/Python in scriptNodes and 'onload' triggers, and malicious scenes have historically spread Maya-targeting malware (e.g. the 'CgAbBlanket'/ vaccine incidents). Open untrusted .mb files with script execution disabled and keep Maya's security/vaccine tools current; the binary form also makes such payloads harder to spot than in text .ma.
Format details
in a nutshell- MapBasic compiled program (MapInfo) - Compiled MapBasic application for MapInfo Professional - unrelated to 3D scenes.
- Multimedia Builder project - Project file for the old Multimedia Builder authoring tool; legacy and unrelated.
- Database / mailbox backup files - Some apps use .mb for generic database or mailbox data; niche and unrelated.
Programs that open MB files
Windows1 app
Autodesk Maya
Paid File > Open Scene and select the .mb. The only app that opens binary scenes faithfully; free 30-day trial and student licences exist. 
macOS1 app
Autodesk Maya
Paid File > Open Scene and pick the .mb (macOS build available). Free trial/student licence to open it once. 
Linux1 app
Autodesk Maya
Paid Open the .mb in Maya for Linux (the studio/VFX standard platform). Then export to FBX/Alembic if needed. Technical details
deep spec| Container format | IFF FORM/LIST chunk hierarchy - FOR4 group chunks for 32-bit files, FOR8 for 64-bit large-scene files |
| Magic bytes | `FOR4` (46 4F 52 34) at byte offset 0 for standard files; `FOR8` (46 4F 52 38) for the 64-bit variant |
| Encoding | Binary - not human-readable or editable in a text editor |
| Byte order | Big-endian, following IFF convention |
| Compression | None - geometry, animation curves and attribute data are stored uncompressed within chunks |
| MIME type | `application/octet-stream`; also recognized as `application/x-maya-binary` |
| Typical file size | 1 MB to several GB depending on scene geometry, texture references and cached animation |
| Platform support | Windows, macOS, Linux |
| 32-bit file size limit | ~2 GB (FOR4 FORM variant - chunk lengths stored as 4-byte values) |
| 64-bit large-scene variant | FOR8 FORM - lifts the 2 GB cap by storing chunk lengths as 8-byte values; introduced in Maya 2014 |
| Internal data model | Maya dependency graph encoded as a hierarchy of typed nodes, attributes, connections and animation curves |
| Default save format | Yes - Maya saves scenes as `.mb` by default rather than the ASCII `.ma` format |
| Text-format counterpart | `.ma` (Maya ASCII) encodes the same scene data as human-readable MEL-like text; `.mb` is more compact and loads faster |
| Released | 1998 (Maya 1.0) |
| Latest version | FOR8 64-bit variant since Maya 2014 (for scenes over 2 GB) |
| Specification | help.autodesk.com |
MB conversions
Community Q&A
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