GeoJSON Validator & Fixer

Field guide: GeoJSON Validator & Fixer

GeoJSON fails quietly: the map renders nothing, or your points appear in the Southern Ocean, and the JSON itself looks perfectly plausible. This validator checks structure against RFC 7946 — root type, Feature wrappers, geometry types, coordinate arrays, ring closure — and, critically, the mistakes the spec can't see but experience can: coordinates in [latitude, longitude] order (the #1 GeoJSON bug; the spec demands [lon, lat]), values out of range, missing properties members, and the legacy crs member that modern parsers ignore or reject.

Where a fix is mechanical and safe, it's applied automatically and offered as a download: swapped coordinate pairs are flipped (detected when |lat-position| > 90 — unambiguous), unclosed polygon rings get their first position appended, missing properties become null. Anything ambiguous stays a warning for you to judge. Errors are reported with JSON paths (features[3].geometry ring 0.1[7]) so you can find the offending vertex in a 10,000-line file. Validation is local — paste proprietary data freely.

Field tips

• Points in the ocean off west Africa (0,0) or features mirrored into the wrong hemisphere = coordinate order. GeoJSON is [longitude, latitude] — x before y, like maths, unlike speech.
• A 'valid with warnings' file usually renders fine — warnings flag spec deviations (open rings, crs member) that strict parsers like Mapbox GL or PostGIS may still reject.
• Validate before you upload anywhere: GitHub's map preview, Mapbox and Leaflet all fail differently on the same broken file, which makes debugging by upload slow.

Conversions run locally in your browser and follow the cited specifications. Always verify critical output in the target application; for survey-grade or legal data, confirm coordinate systems and datums with your GIS team.