What an open path means
A visible shape can look closed without being closed in the file.
SVG paths are sequences of drawing commands. A contour can end near its starting point without using a close command, and a line or polyline is open by definition. For cutting or joining workflows that may matter: a tiny endpoint gap can interrupt a contour even when it is hard to see at normal zoom.
Open geometry is not automatically an error. Score lines, engraving strokes, fold marks and construction lines can intentionally stay open. That is why this checker reports evidence for review instead of converting every open path into a closed shape.
Near-gap tolerance
Millimetre gap checks need a reliable physical scale.
The near-gap setting is expressed in millimetres. To compare SVG endpoints against that tolerance, the file needs enough dimension and viewBox information to resolve SVG units to physical size. If that scale is ambiguous, the checker says so rather than pretending a coordinate-unit distance is a millimetre distance.
Choose a tolerance that makes sense for your own process and inspect the highlighted finding in the source file. The checker does not know your machine precision, material behavior or whether two nearby endpoints were meant to join.
For sizing problems use SVG Size & Units Checker. For a wider structural review use Fabrication Doctor.
