What is the MPX file format?
.mpx (Microsoft Project Exchange) is a plain-text, comma-delimited format for exchanging project management data between scheduling applications. Microsoft introduced .mpx with Project 4.0 in 1994 as an interchange standard allowing project data to be shared with third-party tools unable to read the native binary .MPP format.
An .mpx file consists of a sequence of numbered record types, each separated by CR+LF line endings. Each record begins with a numeric record-type identifier followed by comma-separated positional field values. Key record types include the project header (record 1), working calendars (record 7), task definitions (records 60-70), resource assignments (record 75), and resource records (records 140-150). The file encoding is 7-bit ASCII, and the format version is declared in record 1, field 4; MPX 4.0 is the last defined version.
Microsoft Project 98 was the last version to write .mpx natively; Project 2000 and later dropped export in favor of an XML-based format. Despite this, .mpx was widely adopted by third-party project management tools including Primavera, OmniPlan, Sciforma, and RationalPlan. The open-source Java library MPXJ remains the most capable read/write implementation available today.
.mpx has been effectively superseded by the Microsoft Project XML format for interchange and .mpp for native storage, but it remains in use as a lowest-common-denominator exchange format supported by virtually every scheduling tool.
Security & safety
RISK: LOWPlain ASCII text; no macros or executable content. Safe to open and inspect in any text editor.
Format details
in a nutshellPrograms that open MPX files
Windows4 apps
Microsoft Project
Paid File > Open > select .mpx file. Supported for import through Project 2010; later versions may require conversion. 
MPXJ (Java library/CLI)
Open-source Command-line: java -jar mpxj.jar input.mpx output.xml (also converts to JSON, Excel, etc.) 
macOS2 apps
Linux2 apps
Technical details
deep spec| Encoding | 7-bit ASCII text; some implementations extend to 8-bit for locale-specific characters |
| Container | Plain-text comma-separated records (MPX schema); no binary elements |
| Line terminator | CR+LF (\r\n) |
| Record structure | Each record begins with a numeric record-type identifier followed by comma-separated positional field values |
| Key record types | 1 (File Creation/Header), 7 (Calendar), 60-70 (Tasks), 75 (Resource Assignments), 140-150 (Resources) |
| Format version | MPX 4.0 - declared in File Creation Record (record 1), field 4; final known version |
| Last native write support | Microsoft Project 98 (1997); Project 2000 and later support import only |
| Typical file size | 10 KB - 5 MB |
| Compression | None - plain ASCII text with no compression layer |
| Encryption | None - contents are human-readable plain text |
| Third-party library | MPXJ (open-source Java) - most capable MPX read/write implementation, actively maintained |
| Superseded by | Microsoft Project XML format (since Project 2000) for interchange; .MPP for native storage |
| Released | 1994 (Microsoft Project 4.0) |
| Latest version | MPX 4.0 (last written by Microsoft Project 98) |
| Specification | docs.fileformat.com |
MPX conversions
Community Q&A
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