Blanking applied by a conditional rule

How the text is hidden

Excel's conditional formatting applies a differential format — a <dxf> in xl/styles.xml — on top of a cell's static one. A <dxf> may carry its own <numFmt>, and a blank-rendering code there empties the cell exactly as it does in cellXfs, while the value stays in <v> or the shared-string table. The link is indirect: <conditionalFormatting sqref="…"> in the worksheet names a range, and a <cfRule dxfId="N"> inside it points at the differential format. Reachable entirely by clicking: New Rule, use a formula, format, custom, ;;;.

Why a model still reads it

A reader sees the rule's result; a parser sees neither. Text extraction reads the stored value and does not evaluate conditional formatting, so the cell reaches a model with its contents intact.

What we do about it

readBlankingDxfs walks <dxfs> and records the index of every <dxf> whose formatCode passes the same rendersBlank test the static path uses — keyed on the dxf's content, not on conditional formatting merely being present. readConditionalBlanks then collects the sqref ranges of any <conditionalFormatting> block whose <cfRule> points at one of those indices, and a cell inside such a range gets the invisible reason conditional-blank-format. The rule xlsx-conditional-blank-format reports at severity high with action flag — the value is left in the canonical text, unlike its static twin. visibilityOf grades it 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.