word-docx

Structure

• DOCX is a ZIP containing XML files—word/document.xml has main content, word/styles.xml has styles
• Text splits into runs (<w:r>)—each run has uniform formatting; one word may span multiple runs
• Paragraphs (<w:p>) contain runs—never assume one paragraph = one text block
• Sections control page layout—headers/footers, margins, orientation are per-section

Styles vs Direct Formatting

• Styles (Heading 1, Normal) are named and reusable—direct formatting is inline and overrides style
• Removing direct formatting reveals underlying style—useful for cleanup
• Character styles apply to runs, paragraph styles to paragraphs—they layer together
• Linked styles can be both—applying to paragraph or selected text behaves differently

Lists & Numbering

• Numbering is complex: abstractNum defines pattern, num references it, paragraphs reference numId
• Restart numbering not automatic—need explicit <w:numPr> with restart flag
• Bullets and numbers share the numbering system—both use numId
• Indentation controlled separately from numbering—list can exist without visual indent

Headers, Footers, Sections

• Each section can have different headers/footers—first page, odd, even pages
• Section breaks: next page, continuous, even/odd page—affects pagination
• Headers/footers stored in separate XML files—referenced by section properties
• Page numbers are fields, not static text—update on open or print

Track Changes & Comments

• Track changes stores original and revised in same document—accept/reject to finalize
• Deleted text still present with <w:del> wrapper—don't assume visible = all content
• Comments reference ranges via bookmark IDs—<w:commentRangeStart> to <w:commentRangeEnd>
• Revision IDs track who changed what—metadata persists even after accepting

Fields & Dynamic Content

• Fields have code and cached result—{ DATE \@ "yyyy-MM-dd" } vs displayed date
• TOC, page numbers, cross-references are fields—update fields to refresh
• Hyperlinks can be fields or direct <w:hyperlink>—both valid
• MERGEFIELD for mail merge—placeholder until merge executes

Compatibility

• Compatibility mode limits features to earlier Word version—check w:compat settings
• Page size defaults vary by tool and region—set US Letter vs A4 explicitly or pagination and table widths can drift
• LibreOffice/Google Docs: complex formatting may shift—test roundtrip
• Embedded fonts may not transfer—fallback fonts substitute
• DOCM contains macros (security risk); DOC is legacy binary format

Common Pitfalls

• Empty paragraphs for spacing—prefer space before/after in paragraph style
• Manual page breaks inside paragraphs—use section breaks for layout control
• Images in headers: relationship IDs are per-part—same image needs separate relationship in header
• Copy-paste brings source styles—can pollute style gallery with duplicates