GeoJSON is an open standard format (RFC 7946) for encoding geographic data structures using JSON. It supports geometry types like Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection. GeoJSON is widely used in web mapping applications (Leaflet, Mapbox, Google Maps), GIS software (QGIS, ArcGIS), and spatial databases (PostGIS, MongoDB). Each feature can include properties for storing non-spatial attributes, making it ideal for everything from simple location markers to complex administrative boundaries.

RFC 7946 is the IETF standard that defines the GeoJSON format (published August 2016). Key requirements include: coordinates must use WGS 84 (EPSG:4326) with longitude first [-180, 180] then latitude [-90, 90]; Polygon rings must be closed (first and last coordinates identical); the top-level object must be a Feature, FeatureCollection, or geometry; and the type field is mandatory at every level. Our validator checks all these rules and reports any violations with specific fix suggestions.

GeoJSON requires Polygon rings to be "closed," meaning the first and last coordinate pairs must be identical. This explicitly signals that the ring forms a closed loop. A Polygon ring must have at least 4 coordinate pairs (3 distinct points plus the closing duplicate). For example: [[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]. If your ring isn't closed, many GIS tools will fail to render it correctly or may misinterpret the geometry. Our validator flags unclosed rings as errors.

Yes! According to RFC 7946, a Feature's geometry can be null. This is useful for representing entities that have properties but no known spatial location yet, or for features that are purely attribute-based. However, a Feature must have a properties key (which can be null or an empty object {}). Our validator correctly handles null geometries and won't flag them as errors.

GeoJSON exclusively uses the WGS 84 coordinate reference system (EPSG:4326). Coordinates are specified as [longitude, latitude] — note that longitude comes first, which is the opposite of the common "latitude, longitude" convention. Longitude must be between -180 and 180, and latitude between -90 and 90. Altitude (elevation) can optionally be included as a third element. If you're converting from other formats like shapefiles or KML, make sure to reproject to WGS 84 first.

Our online validator works best with files up to ~10 MB. For very large datasets (hundreds of thousands of features), browser performance may degrade. We recommend splitting large files into smaller chunks for validation. The tool provides real-time feedback on character count and estimated file size, and will warn you if the input exceeds 5 MB. For production-grade large dataset validation, consider using command-line tools like geojsonhint or ogr2ogr with validation flags.