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Microsoft Excel workbook comparison

The bundled Excel adapter ports TortoiseGit's diff-xls.js. It opens captured base/new workbooks in Excel and adds conditional formatting to the new copy so changed cell values appear red. The view keeps Excel formulas, worksheets and formatting; it is not a plain-text or metadata-only export. Microsoft Excel must be installed separately.

New unsaved Diff Viewer defaults include .xls, .xlsx, .xlsm, .xlsb and .xlam. Existing saved choices remain authoritative. Settings → Diff Viewer → Advanced → Restore Defaults restores bundled associations while retaining other records. Accept Advanced and Apply Settings. The program editor offers Microsoft Excel workbook comparison and Microsoft Excel workbook comparison (fast). The full mode is the default. Shift bypasses an enabled association to retain the ordinary internal byte/text view. Excel adapters are not merge tools.

Full and fast modes

Worksheets pair by position, as upstream does. Full mode copies matching base worksheets into the new workbook as uniquely named Dummy_for_Comparison… reference sheets with gray tabs. Fast mode avoids those copies and uses references to the open base workbook; keep both workbooks open. Workbook protection or an uncopyable sheet can fall back to fast references with a warning.

Normally visible tabs lose their special color. Hidden worksheets are unhidden and marked green where structure protection permits. Protected contents cannot receive conditional formatting and are reported. Existing conditional formatting in the private new copy is replaced with the red comparison rule. Native formula conversion uses an owned scratch workbook, which is then closed. Sheet/workbook names are quoted inside the reference formula; they never become script syntax. The matching cells compare values, so distinct formulas with equal values are not highlighted. Newly added sheets mark their used cells red; extra base sheets remain visible in the base workbook. These edge policies need live Excel acceptance.

The adapter tries to stack only the two comparison windows horizontally. The Windows-only synchronized-side-by-side API has no matching command in the inspected Mac dictionary; synchronized scrolling remains open. Protection/layout failures are reported rather than preventing all comparison. A native warning window shows up to ten source-style numbered warnings plus a remaining count. Its text is selectable and scrollable, with light/dark appearance and OK/Escape.

Inputs, permission and lifetime

Input bytes are captured exactly in private read-only files with distinct role prefixes. Source/original workbooks are never rewritten, staged or saved by the adapter. Excel's automatic macros are disabled for opening and the prior security value is restored on success/error where Excel responds. Existing external links are not refreshed during opening. The source's saved-state behavior suppresses an unwanted Save As prompt for these comparison copies. Other user workbooks are not closed and Excel is never terminated on cancellation or failure.

Paths and the full/fast flag arrive as Apple-event descriptors to a fixed handler. Preparation runs off the UI thread; the Excel worker is serialized. Cancellation before dispatch suppresses it. An already dispatched operation cannot be rolled back; actual worker/Quit ownership lasts until its callback settles. A retired owner does not open a late warning or report an obsolete error. Success or a possibly opened/uncertain failure retains copies through normal app cleanup; confirmed denied/unopened failure removes them. Saved Data → Temp files or OS cleanup can remove retained copies later.

macOS Automation permission is required. Denial provides the System Settings → Privacy & Security → Automation recovery hint. The AppStore preparation profile requests a target-specific Excel exception, alongside Word; the installed Office dictionaries declare no scripting access groups. Mail retains its compose-only target. This follows the mechanism documented by Apple, with exception use cases still required for eventual review. Source declarations and unsigned audits do not prove signed sandbox or App Store acceptance.

Acceptance still open

Core/native checks distinguish exact snapshots, mode/descriptor dispatch, warning presentation, permission failure and retired-worker lifetime from live Excel behavior. The local optional terminology check compiles the fixed handler without executing workbook operations. It does not prove conditional-format rendering, locale/formula handling, protected workbooks, macro policy, every format or actual TCC/file grants. Those checks, synchronized scrolling, physical UI/VoiceOver, signed Finder/AppStore and full upstream parity remain open.

Native warning appearance

These captures show the shipping TurtleGit warning window with injected protected- sheet warnings. They verify readable native light/dark presentation, not live Excel comparison output.