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.
All seven nonempty, structurally supported 2D GeoJSON geometry types reach GEOS, including nested GeometryCollections. Points require two finite coordinates, lines at least two positions, and polygon rings at least four positions with explicit closure. Collections retain one result per source record. The tool does not change or repair input.
Validation approach
Sixteen self-authored fixtures cover points, repeated multipoints, lines, MultiLineStrings, nested GeometryCollections, 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.
Attribute method
Configured attribute checks use an independent local checker, without GEOS or value coercion. Required/null/empty checks precede strict types; type failures skip dependent content checks, while all applicable content constraints are reported. AR-001–AR-003 describe these categories; AR-004/AR-005 describe attribute sources and configuration, and AR-006 checks Feature identification independently of field-source availability. Identity issues have no configured field-rule reference.
Attribute regression fixtures have hand-authored expectations. QGIS parity covers spatial results and does not independently validate custom attribute rules or DBF attributes.
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 or collection. GEOS validity is separate from simplicity: crossing lines and repeated points can be valid. Collapsed lines with fewer than two distinct positions are invalid. A valid result does not establish business correctness, CRS correctness or topology between features.
Duplicate geometry rule
The optional duplicate geometry check compares valid planar 2D points, lines and polygons within one file using topological equality. Vertex order, extra collinear vertices, attributes and feature IDs do not determine equality. MultiPoint, MultiLineString and MultiPolygon participate; GeometryCollection is excluded. No tolerance, snapping or repair is applied. Each unordered pair of duplicate source records produces one topology problem. With three equal records there are three pairs. Downloads contain all pairs and the run configuration; the record table shows each record's related pairs. Skipped comparisons and partial coverage are reported explicitly. Overlaps, gaps, line simplicity and network connectivity are not covered by this rule.