What is the GAN file format?
A .gan file is a project file created by GanttProject, free open-source project-scheduling software written in Java. The application is used for planning and scheduling projects using Gantt charts and resource management.
A .gan file stores all elements of the project, including tasks with durations and dependencies, project resources and their allocations, deadlines, calendars, and view settings. Internally it is a plain UTF-8 XML document whose root element is <project>, followed by <tasks>, <resources>, <allocations> and <calendars> sections - so the file can also be inspected or edited in any text editor. Because the format uses no compression or encryption, file sizes typically range from a few kilobytes to a few hundred kilobytes depending on project complexity.
The .gan format interoperates with Microsoft Project files via GanttProject's built-in import and export. Projects can also be exported to CSV for spreadsheet use or to PDF for sharing printed Gantt charts.
GanttProject and the .gan file format are supported on Windows, Linux, and macOS - any platform with a Java runtime.
Security & safety
RISK: LOWA .gan file is plain XML data with no executable code, so opening one is safe. The only caution is the usual XML/external-reference hygiene: a web-link attribute is just text. As always, verify the file is really XML (not an executable renamed .gan) before opening from an untrusted source.
Format details
in a nutshellPrograms that open GAN files
Windows2 apps
GanttProject
Open-source Install GanttProject (free), then File -> Open and select the .gan. It renders the tasks as a Gantt chart you can edit. 
Text editor (inspect only)
Open-source Open the .gan in Notepad++ to read the raw XML (tasks, resources). For viewing only - editing in the app is safer. 
macOS1 app
GanttProject
Open-source Install the macOS build (requires Java/bundled runtime), then File -> Open the .gan. 
Linux1 app
Technical details
deep spec| Encoding | UTF-8 plain text (XML) |
| Container format | Single XML document; root element is `<project>` |
| MIME type | application/xml (also accepted as text/xml) |
| Compression | None - file is uncompressed plain text |
| Typical file size | A few KB to a few hundred KB, depending on task and resource count |
| Document sections | `<tasks>`, `<resources>`, `<allocations>`, `<calendars>` plus view-configuration data |
| Root element attributes | name, company, view-date and webLink stored as XML attributes on `<project>` |
| Task model | Hierarchical tasks with duration, start date, percent-complete, milestone flag and predecessor dependencies |
| Resource model | Named human resources with roles, e-mail and allocation percentages per task |
| Calendar support | Custom work calendars per project with weekend and holiday exceptions |
| Schema versioning | Format version stored as an attribute in the file; 2.x and 3.x project files are backward-compatible |
| Platform requirement | Cross-platform; requires a Java runtime (Windows, macOS, Linux) |
| Interoperability | Import and export to Microsoft Project (.mpp/.mpx), CSV and PDF from within GanttProject |
| Developer / maintainer | GanttProject Team (BarD Software); free open-source under GNU GPL |
| Identification | No binary magic number; identified by XML declaration and `<project>` root with GanttProject-specific attributes |
| Released | 2003 (GanttProject 1.x) |
| Latest version | GanttProject 3.x XML project format (current) |
| Open standard | Yes · royalty-free |
| Specification | www.ganttproject.biz |
GAN conversions
Community Q&A
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