Cells parked outside the used range

How the text is hidden

A worksheet declares its used range in <dimension ref="A1:D20"> — the region Excel scrolls to and sizes its scrollbars against. A cell written outside that declared range is an ordinary <c> element in <sheetData> with an ordinary value. The engine applies no distance margin: a cell one column past the declared range is judged outside it exactly as one parked at BZ4000 is, so a workbook whose writer emits an under-sized <dimension> is reported on the same footing as one where the parking was deliberate.

Why a model still reads it

<dimension> is a hint about presentation. Cell readers iterate <sheetData> rows and return every <c> they find, in document order, with no reference to the declared range.

What we do about it

readDimension parses the <dimension ref> into row and column bounds, and each cell's own r reference is tested against them by withinDimension. A cell outside gets geometry.onCanvas: false and the invisible reason off-canvas; the rule xlsx-offrange-content reports at severity high, action flag. visibilityOf grades off-canvas as never.

How often it fires

0% of 200 real workbooks from five national open-data portals (CA, IE, DE, GR, UK), measured 2026-08-21.

This is an alert-volume number and nothing else. It says how often the alarm sounds on documents as found — not how often it is right, and not whether what it found was harmless. Documents as found may themselves carry concealment. Read it against the population named above rather than as a property of documents in general.