What is the NMF file format?
An .nmf file is a JSON manifest used by Google Native Client (NaCl), a now-deprecated browser technology that allowed compiled C and C++ programs to run inside the Chrome sandbox. The manifest tells the browser which native executable to load for each CPU architecture, so the correct binary is fetched and launched at runtime.
The file is plain UTF-8 JSON beginning with {, and typically contains a "program" key mapping architecture names (x86-32, x86-64, arm) to URLs of .nexe native executable files. An optional "files" key lists additional data assets the module requires. For Portable Native Client (PNaCl) applications, an "interpreter" key references a .pexe portable executable instead of architecture-specific binaries.
Google introduced NaCl in 2011 as part of the Native Client SDK for Chrome. The technology was deprecated for non-ChromeOS platforms in 2017, superseded by WebAssembly, which delivers equivalent near-native performance with full cross-browser support. Chrome removed NaCl support on non-ChromeOS systems in 2022. ChromeOS Kiosk Apps built on NaCl continue to receive support until October 2028 per Google's published deprecation schedule.
.nmf files can be opened and inspected in any text editor. They are historically associated with desktop GIS tools such as ArcGIS Desktop, which used NaCl-based plugins on certain platforms.
Security & safety
RISK: LOWNMF manifest files are plain JSON text - no executable content. The referenced .nexe binaries are the executable components and were sandboxed by Chrome's NaCl sandbox.
Format details
in a nutshell- ArcGIS Explorer Map File (ESRI) - Map project/basemap configuration file created by ArcGIS Explorer, a free GIS viewer by ESRI; stores map layers, extent, and service references.
- NICE Media File (NICE Systems) - Proprietary audio recording file format used by NICE Systems contact center recording software (NMF = Nice Media File); contains recorded call audio with metadata.
- LightWave Normal Map File - Normal map file created by LightWave 3D (NewTek/LightWave Digital); stores surface normal vector data for 3D rendering.
Programs that open NMF files
Windows3 apps
Notepad / any text editor (NaCl manifest)
Built-in Open .nmf in Notepad or VS Code to inspect JSON structure.
ArcGIS Explorer (ESRI)
Free (discontinued) File → Open - opens .nmf map files (ArcGIS Explorer format). DISCONTINUED - retired by ESRI; use ArcGIS Earth instead. Technical details
deep spec| File format | UTF-8 JSON text |
| File signature | Begins with `{` (standard JSON object opening) |
| Required key | `"program"` - maps CPU architecture names to `.nexe` executable URLs |
| Optional key: files | `"files"` - maps named file identifiers to URLs for data assets |
| PNaCl support | `"interpreter"` key references a `.pexe` portable executable for architecture-independent deployment |
| Architecture targets | `x86-32`, `x86-64`, `arm` - keys within the `"program"` object |
| Transport security | Relies on HTTPS; no in-file checksum or cryptographic signature |
| Typical file size | 1 KB - 20 KB |
| MIME type | application/json |
| Platform support | Chrome browser (all OS) - NaCl removed from non-ChromeOS Chrome in 2022; ChromeOS extended to October 2028 |
| Technology status | Deprecated 2017 for non-ChromeOS; Chrome support removed 2022 on non-ChromeOS |
| Superseded by | WebAssembly (.wasm) |
| Released | 2011 (Google Native Client SDK) |
| Open standard | Yes · royalty-free |
| Specification | developer.chrome.com |
NMF conversions
Community Q&A
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