Convert FlatGeobuf to GeoJSON Online — Free GIS Converter

FlatGeobuf is optimized for fast machine reads, but GeoJSON is what web maps, open-data platforms, and human developers actually work with — convert your .fgb file to a readable, portable .geojson file with geodata.plus.

Why convert FlatGeobuf to GeoJSON?

FlatGeobuf is an excellent format for storing and serving large vector datasets efficiently, but it is a binary format that cannot be inspected in a text editor, previewed on GitHub, or pasted into a web map without a specialized reader. GeoJSON is the universal currency of web GIS — Leaflet, Mapbox GL, OpenLayers, Deck.gl, and GitHub all render GeoJSON natively without any additional tooling.

When you need to share a FlatGeobuf dataset with a colleague who does not have GDAL or QGIS, publish data to an open-data portal, or quickly visualize features in a browser map, converting to GeoJSON is the fastest path. It also makes the data diff-able in version control, since JSON changes are human-readable.

Why use geodata.plus

• Free tier — convert up to 3 files per month at no cost, no credit card required
• Automatic CRS detection — reads the CRS stored in the FlatGeobuf header and handles reprojection automatically
• Optional reprojection — reproject from any source EPSG to WGS 84 (EPSG:4326) or any other target CRS before download
• Browser-based — no QGIS, GDAL, or Node.js install needed; works on any modern browser
• Encrypted transfer — all uploads use TLS; files are stored temporarily in Cloudflare R2 and automatically deleted on schedule
• Auto-deleted output — output files are automatically deleted after 2 days (free tier) and 7 days (Pro); no manual cleanup needed

How it works

1. Upload your FlatGeobuf file (.fgb) using the widget above
2. geodata.plus reads the FlatGeobuf header to detect the CRS and geometry type automatically
3. Select GeoJSON as the output format; optionally choose a target EPSG if reprojection is needed
4. Download your .geojson file ready for web mapping, open-data publishing, or version control

FlatGeobuf format

FlatGeobuf is a binary, row-oriented vector format built on the FlatBuffers serialization library. It includes a packed Hilbert R-tree spatial index at the start of the file, enabling fast spatial queries and HTTP range request streaming. FlatGeobuf stores the CRS in its header, supports all OGC geometry types, and imposes no field name restrictions. It is the fastest single-file vector format for read-heavy GIS workflows.

| Property | Value | |---|---| | Extension | .fgb | | Type | Vector, single file (binary) | | Coordinate system | Any CRS (stored in header) | | Geometry types | Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, GeometryCollection | | Common software | GDAL, QGIS, Mapbox, cloud-native GIS, web APIs |

GeoJSON format

GeoJSON is an open standard (RFC 7946) for encoding geographic features in JSON. All coordinates must be in WGS 84 (EPSG:4326) per the specification. GeoJSON supports points, lines, polygons, and their multi-part equivalents, with arbitrary key-value properties per feature. It is human-readable, diff-able in version control, and natively rendered by GitHub, Mapbox, and Leaflet without any additional library.

| Property | Value | |---|---| | Extension | .geojson, .json | | Type | Vector, single file | | Coordinate system | Always WGS 84 (EPSG:4326) | | Geometry types | Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon | | Common software | Leaflet, Mapbox, OpenLayers, QGIS, ArcGIS, GitHub |

Frequently asked questions

FlatGeobuf files can be very large — will the conversion handle big datasets?

geodata.plus streams the FlatGeobuf file using its built-in spatial index rather than loading the entire dataset into memory at once. Datasets up to several hundred megabytes are handled efficiently. For very large files (multiple gigabytes), consider using GDAL's ogr2ogr command-line tool for batch processing.

My FlatGeobuf is in a projected CRS, not WGS 84 — will the GeoJSON output be valid?

Yes. geodata.plus reads the CRS from the FlatGeobuf header and reprojects coordinates to WGS 84 (EPSG:4326) as required by the GeoJSON RFC 7946 specification. The output will be valid GeoJSON regardless of the source CRS.

Does the conversion preserve all attribute columns from the FlatGeobuf file?

Yes. FlatGeobuf stores a full attribute schema in its header, and geodata.plus maps all columns directly to GeoJSON feature properties, preserving column names, types (string, integer, float, boolean), and values without truncation or modification.