Method and validation
Engine and interpretation
The pinned geos-wasm package is 3.1.1, containing GEOS 3.13.0 (C API 1.19.0). Checks use validity flags 0. Coordinates are interpreted in a 2D plane; no reprojection or spherical interpretation is performed.
Only structurally supported, nonempty Polygon and MultiPolygon geometries reach GEOS. Rings must have at least four positions and be closed. The tool does not change or repair input.
Validation approach
Eight self-authored fixtures cover valid polygons, self-intersection, hole errors, repeated vertices, degeneration and MultiPolygons. Real WASM tests and same-version native GEOS parity tests compare validity and allowed error locations with a 1e-9 tolerance; reason strings need not match verbatim.
Current evidence and limits
Core, real-engine and native parity checks are reproducible from the repository. Browser interaction, network privacy, desktop browser compatibility and performance have separate acceptance checks. A successful build alone does not establish those results. The current build is a development preview pending full browser and distribution review.
Only the first validity reason is returned for each geometry. A valid result does not establish business correctness, CRS correctness or topology between features.