What is the PRM file format?
.prm is a generic parameter file extension reused independently by many unrelated applications across scientific computing, optimization, simulation, and other technical fields. It has no single author, format definition, or universal structure.
In most cases, .prm files are plain-text documents containing named parameters - either as key/value pairs, whitespace-delimited columns, or application-specific syntax. Notable users include GSAS and GSAS-II (crystallography), where .prm files store X-ray or neutron instrument parameters used in powder diffraction refinements, and Gurobi Optimizer, where .prm files hold solver option settings that tune the optimization algorithm. Some programs store binary parameter data under the same extension.
Because the extension is generic, the correct way to open a .prm file depends entirely on which application created it. A GSAS instrument parameter file is completely unrelated to a Gurobi solver options file despite sharing the extension. Other known users include TomTom GPS navigation maps, the Re-Volt car-physics game engine, and older versions of Adobe Premiere.
Most .prm files can be inspected in any plain-text editor to identify the originating application from internal comments or structure. Binary variants will appear as garbled output and must be opened only with their native program. Related generic configuration formats include .par, .cfg, and .ini.
Security & safety
RISK: LOWA .prm is settings data, not an executable, so opening one is generally safe. Editing parameters can change how the host program behaves (e.g. a refinement or a solver run), so keep a backup before changing values. Treat unknown binary .prm files with normal caution.
Format details
in a nutshell- TomTom Map Parameter File - Settings/parameter file used inside a TomTom navigation map folder (not user-openable).
- Re-Volt Car Parameters - Text file defining a car's physics/stats in the racing game Re-Volt.
- Adobe Premiere Project (legacy .prm plug-in) - Adobe Premiere uses .prm for importer/exporter plug-in modules, not media.
Programs that open PRM files
Windows3 apps
Gurobi Optimizer
Paid Use model.read('file.prm') / GUROBI ReadParams to load a solver parameter file. 
Notepad
Open-source Open a text-based .prm to read or edit its parameters and identify the source program.
GSAS / GSAS-II
Free Load the instrument parameter (.prm) inside GSAS-II when setting up a refinement. 
macOS2 apps
Linux2 apps
Technical details
deep spec| File type | Generic application parameter/configuration file |
| Developer | Various (no single vendor; extension reused independently) |
| Encoding | Text (ASCII/UTF-8) in most cases; binary for some applications |
| Container | Plain text (typical) or application-specific binary |
| Typical file size | 1 KB - 1 MB |
| Magic bytes | None; no universal signature - identify by the creating application |
| Notable users | GSAS/GSAS-II (crystallography instrument parameters), Gurobi Optimizer (solver settings), TomTom GPS, Re-Volt game engine |
| Content structure | Named parameters as key/value pairs, whitespace-delimited columns, or application-specific syntax |
| Versioning | Entirely application-defined; no shared versioning scheme across users of the extension |
| MIME type | text/plain (for text variants); application/octet-stream (for binary variants) |
| Associated OS | Windows, Linux, macOS |
| Identification method | Must be identified by the originating application context, not by extension alone |
| Released | N/A (generic extension reused by many programs over decades) |
| Latest version | N/A (defined by each host application) |
PRM conversions
Community Q&A
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