What is the GML file format?
.gml files store data encoded in the Geography Markup Language. It is a formal language developed by the Open Geospatial Consortium (OGC), and it is based on the eXtensible Markup Language (XML). Its main purpose is to encode and transfer geographic data, including geometry, topology, and feature attributes. Rules regarding data storing within a .gml file are defined in the ISO 19136 norm (first edition 2007, second edition 2020).
Files saved in the .gml format enable exchange of data containing geographic information between different platforms and software. Because .gml is plain-text XML, every file opens with an <?xml ...?> declaration followed by GML namespace declarations - for example xmlns:gml="http://www.opengis.net/gml/3.2". Geometries such as points, lines, polygons, and solids are described using GML elements, each tied to a coordinate reference system via the srsName attribute (typically an EPSG code). GML also supports temporal objects and three-dimensional coordinates, capabilities that go beyond simpler geospatial formats such as KML or GeoJSON.
GML files can be opened, converted, and validated with tools such as QGIS, FME, and the ogr2ogr command-line utility from the GDAL library.
Security & safety
RISK: LOWA Geography Markup Language file is plain-text XML - passive data with no executable content, so it's safe to open in a text editor or load in QGIS. The only practical caution is size: GIS GML files can be very large and slow to open in a plain editor, so use QGIS or GDAL/OGR for big datasets rather than loading the whole XML into Notepad.
Format details
in a nutshell- GameMaker Language (GML) - Plain-text script (source code) for the GameMaker / GameMaker Studio engine, edited in the GameMaker IDE or any code editor.
- Graphlet Graphscript - Legacy graph-drawing tool format; largely historical and rarely encountered today.
Programs that open GML files
Windows3 apps
QGIS
Open-source Free GIS app. Layer > Add Vector Layer, pick the .gml to view the map data; export to other GIS formats. 
FME Form (formerly FME Desktop)
Paid Powerful spatial-data ETL tool; reads GML and converts it to dozens of GIS formats.
Notepad / VS Code
Open-source Open the .gml as text to read the XML directly (good for small files / inspecting the schema). 
macOS1 app
QGIS
Open-source Free GIS app for Mac; add the .gml as a vector layer to view and convert the map data. 
Linux2 apps
GDAL/OGR (ogr2ogr)
Open-source Command line: 'ogr2ogr -f GeoJSON out.geojson in.gml' to read and convert GML map data. Technical details
deep spec| File type | Plain-text XML |
| MIME type | application/gml+xml |
| Character encoding | UTF-8 by default; any encoding declared in the XML prolog is valid |
| File signature | Starts with `<?xml` declaration; root element declares a GML namespace, e.g. `xmlns:gml="http://www.opengis.net/gml/3.2"` |
| ISO standard | ISO 19136, published in two editions (2007 and 2020); covers GML 3.2.x |
| Geometry types | Point, LineString, Polygon, MultiPoint, MultiCurve, MultiSurface, Solid, and topology primitives |
| 3D coordinate support | Yes - Z values natively supported; `srsDimension` attribute on geometry elements indicates 2D or 3D |
| Coordinate reference system | Declared per feature or collection via `srsName` attribute using EPSG codes or OGC URNs (e.g. `urn:ogc:def:crs:EPSG::4326`) |
| Topology support | Yes - GML defines topology primitives: Node, Edge, Face, and TopoComplex |
| Application schema | Domain-specific feature types defined in user-supplied `.xsd` files that import the base GML schema |
| Simple Features profile | SF-0, SF-1, and SF-2 profiles restrict geometry complexity for broader software interoperability |
| Temporal objects | Built-in types `gml:TimeInstant` and `gml:TimePeriod` for time-stamped and time-ranged features |
| Compression | No built-in compression; commonly transferred as `.gz` streams or wrapped in a [ZIP archive](/format/zip) |
| Released | 2000 (OGC); also published as ISO 19136 |
| Open standard | Yes · royalty-free |
| Specification | www.ogc.org |
GML conversions
Community Q&A
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