GPKG to GeoJSON Converter

A GeoPackage (.gpkg) is an OGC standard (12-128r6) for encoding geospatial information in a SQLite database. It was designed to overcome the limitations of Shapefile — no 10-character column name limit, no 2 GB file size cap, multi-layer support, and a single portable file. QGIS, ArcGIS Pro, PostGIS, GDAL, and most modern GIS tools support GeoPackage natively. It is particularly common in offline and mobile GIS applications where a self-contained, cross-platform format is needed.

When you drop a .gpkg file, the browser reads it using the FileReader API directly into memory. A small WebAssembly build of SQLite called sql.js opens the database and queries the geometry layers. A custom JavaScript WKB parser reads the raw binary geometry blobs and converts each vertex to GeoJSON-style [longitude, latitude] coordinate arrays. The result is serialised to a JSON string and offered as a download — entirely without a network request.

All seven base geometry types from the OGC WKB specification are supported: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection. Z (3D), M (measured), and ZM coordinate variants (WKB type codes 1001–3007) are also handled — the extra coordinates are silently dropped since GeoJSON only supports 2D or 3D (longitude, latitude, altitude). Null geometries (features with no spatial data) are output as "geometry": null, which is valid GeoJSON.

RFC 7946 (the GeoJSON standard) requires coordinates to be in WGS 84 geographic coordinates (EPSG:4326), expressed as [longitude, latitude] decimal degrees. This converter outputs coordinates exactly as they are stored in the GPKG — it does not reproject. If your source data is in a projected CRS such as UTM or a national grid, the resulting GeoJSON will contain metre-based easting/northing values that most web mapping libraries will misplace. Use ogr2ogr -t_srs EPSG:4326 to reproject before or after conversion.

In practice, files under 200 MB convert quickly (under 30 seconds on a modern laptop). Files from 200 MB to 500 MB work but may take a minute and consume significant RAM. Files above 500 MB risk running into browser memory limits, especially on devices with 4–8 GB RAM. The converter hard-limits at 1 GB. For larger files, use GDAL (ogr2ogr), which processes data in streaming chunks without loading the entire database into memory. The converter yields to the browser's rendering thread every 500 rows to keep the UI responsive during long conversions.

Yes. After the converter detects all feature layers in the GeoPackage (by querying the gpkg_geometry_columns system table), you can select which layers to include before clicking Convert. Each selected layer produces a separate .geojson file — one download per layer. A "Download All" button appears for multi-layer results. Note that raster tile layers are not supported; only vector feature layers are converted.