Excel Compatibility

SheetKit aims for Excel parity: a workbook that SheetKit writes or edits should open in Microsoft Excel without repair, and a calculation or structural edit should produce what Excel would produce for the same input. SheetKit 1.0 tightened several behaviors for security and correctness. Some of those changes break compatibility with earlier SheetKit releases. They are acceptable only where they match Excel, so this page records each changed behavior next to what Excel did when given the same input.

How this was verified

Each behavior was run twice on the same input: once through the public SheetKit API (Rust crate, current 1.0 branch), and once in Microsoft Excel 16.114 for Mac, driven through AppleScript on 2026-10-23. Formulas were entered into a scratch workbook, and the value or error Excel calculated was read back. Structural edits were made with Excel's own delete and insert commands on a file SheetKit generated, and Excel then saved the result. The saved XML was compared with SheetKit's output for the same edit. Table names and totals rows were set through Excel's list object model.

Status values:

• MATCH: SheetKit and Excel produced the same result.
• DIFFERS: the results differ. The Notes column says whether the difference is deliberate, a security limit, or a defect.
• NOT VERIFIABLE: Excel could not be driven to the same input through AppleScript. The reason is given.
• N/A: the behavior has no Excel-visible effect, or applies only to the Node.js API.

The AppleScript object model is not the Excel user interface. Where the two can disagree (table naming, for example), the table says which one was tested.

Node.js methods follow the Rust names in camelCase (remove_row is removeRow, add_table is addTable). Formula results are the same in both bindings.

Aggregate functions

Test data: A1 empty, A2 = TRUE, A3 = FALSE, A4 = text "3", A5 = 5. B1:B3 empty.

Behavior	SheetKit	Excel	Status	Notes
AVERAGE, SUM, MIN, MAX, COUNT over A1:A5	calculate_all / evaluate_formula: 5, 5, 5, 5, 1	5, 5, 5, 5, 1	MATCH	Booleans, text, and empty cells inside a range argument are ignored.
AVERAGE(B1:B3) (all empty) and AVERAGE(A2:A4) (only booleans and text)	#DIV/0!	#DIV/0!	MATCH
MIN, MAX, SUM over B1:B3	0	0	MATCH	SheetKit returns SUM of an empty range as negative zero (-0.0), which compares equal to 0.
Direct scalar arguments: AVERAGE(TRUE), SUM("3"), SUM(TRUE)	1, 3, 1	1, 3, 1	MATCH	Booleans and numeric text typed directly as arguments are counted.
AVERAGE("x")	#VALUE! from calculate_all	#VALUE!	MATCH	evaluate_formula returns an Err ("cannot convert") instead of an error value.
COUNT(TRUE,"3","x"), COUNT("3"), COUNT(TRUE)	2, 1, 1	2, 1, 1	MATCH	Booleans and numeric text typed directly as COUNT arguments are counted; through references only numbers are counted.

Date functions

Behavior	SheetKit	Excel	Status	Notes
DATE(10000,1,1), DATE(-1,1,1)	#NUM!	#NUM!	MATCH
DATE(0,1,1), DATE(9999,12,31)	1, 2958465	1 (1900-01-01), 2958465	MATCH
DATE(2024,2147483647,1)	#NUM!	#NUM!	MATCH
DATE(2024,1,day) with day = -32768, -5, 32766, 32767	12523, 45286, 78057, 78058	12523, 45286, 78057, 78058	MATCH
DATE(2024,1,day) with day = 32768, 40000, 65536, -40000	78059, 85291, 110827, 5291	78058 for every one	DIFFERS	Excel returned serial 78058 (2113-09-17, the result for day 32767) for every day value tested outside -32768..32767. SheetKit applies the day offset arithmetically and does not reproduce this clamping.
DATE(2024,1,day) with day = 2958101, 2147483647, 4294967296, 1E10, -2147483648	#NUM!	78058	DIFFERS	Same Excel clamping as above. SheetKit returns #NUM! when the result falls outside 1900-01-01..9999-12-31.
EDATE(45000,2147483647), EDATE(45000,-600)	#NUM!, 26738	#NUM!, 26738	MATCH
EDATE(0,0), EDATE(-1,0)	0, #NUM!	0, #NUM!	MATCH	Serial 0 is 1900-01-00; negative serials return #NUM!.
EOMONTH(45000,2147483647), EOMONTH(2958465,0), EOMONTH(2958465,1)	#NUM!, 2958465, #NUM!	#NUM!, 2958465, #NUM!	MATCH
EOMONTH(1,-1), EOMONTH(31,-1)	#NUM!, #NUM!	#NUM!, #NUM!	MATCH	A result before 1900-01-01 is an error.
EOMONTH(0,0), EOMONTH(-1,0), EOMONTH(60,0)	31, #NUM!, 59	31, #NUM!, 59	MATCH
WORKDAY(45000,1E17), WORKDAY(45000,-1E17), WORKDAY(1,1)	#NUM!, #NUM!, 2	#NUM!, #NUM!, 2	MATCH	SheetKit bounds the day count before iterating.
WORKDAY(0,1), WORKDAY(-1,1)	2, #NUM!	2, #NUM!	MATCH

Text functions

Behavior	SheetKit	Excel	Status	Notes
Negative counts: LEFT("abc",-1), RIGHT("abc",-1), MID("abc",1,-1), REPT("a",-1), REPLACE("abc",1,-1,"x")	#VALUE!	#VALUE!	MATCH
Start below 1: MID("abc",0,1), REPLACE("abc",0,1,"x"), REPLACE("abc",-1,1,"x")	#VALUE!	#VALUE!	MATCH
Huge counts: LEFT("abc",1E10), LEFT("abc",1E300), RIGHT("abc",2147483648)	"abc"	"abc"	MATCH
MID past the end: MID("abc",4,1), MID("abc",32768,1), MID("abc",2147483648,1)	""	""	MATCH
MID("abc",1,2147483647)	"abc"	"abc"	MATCH
MID("abc",1,2147483648), MID("abc",1,1E10), MID("abc",1E10,1)	#VALUE!	#VALUE!	MATCH	A start above 2147483648 or a length above 2147483647 is rejected.
REPT result length: LEN(REPT("a",32767)), REPT("a",32768), REPT("ab",1E10)	32767, #VALUE!, #VALUE!	32767, #VALUE!, #VALUE!	MATCH	32767 characters is Excel's cell text limit.
REPLACE("abc",4,1,"x")	"abcx"	"abcx"	MATCH
REPLACE with start or length above 32767: start 32768, 2147483647, 1E10; length 2147483647, 2147483648, 1E10	#VALUE!	#VALUE!	MATCH
LEN of an error argument: LEN(1/0), LEN(REPT("a",32768))	#DIV/0!, #VALUE!	#DIV/0!, #VALUE!	MATCH	Text functions propagate an error argument.

Rounding

Behavior	SheetKit	Excel	Status	Notes
ROUND(1,309), ROUNDDOWN(1,-309), ROUND(123.456,-2)	1, 0, 100	1, 0, 100	MATCH
ROUNDUP(123.456,-400)	#NUM!	#NUM!	MATCH
ROUND(1.7E308,-308)	#NUM!	Formula cannot be entered	NOT VERIFIABLE	Excel rejects the literal 1.7E308 (its largest numeric literal is about 9.99999999999999E+307), and AppleScript left the cell empty. SheetKit accepts the literal and returns #NUM! because the rounded result overflows.
ROUND(9E307,-307), ROUND(9.9E307,-307)	9.000000000000004E+307, 1.0000000000000004E+308	9E+307, 1E+308	DIFFERS	Floating-point error at extreme magnitudes. The relative error is about 4E-16.

TEXT number formats

Behavior	SheetKit	Excel	Status	Notes
TEXT(1.25,"# ?/8")	"1 2/8"	"1 2/8"	MATCH
TEXT(1,"0E+0"), TEXT(1,"ʼn0")	"1E+0", "ʼn1"	"1E+0", "ʼn1"	MATCH
TEXT(1,"ʼnE+é")	"1E+0"	#VALUE!	DIFFERS	Security limit. SheetKit always produces finite, bounded output for any format code and does not reject every code Excel considers invalid.
TEXT(42949672964294967296,"/?"), TEXT(1E15,"/?")	"42949672964294970000", "1000000000000000 "	#VALUE!, #VALUE!	DIFFERS	Security limit, as above.
TEXT(1.5,"?/18446744073709551615"), TEXT(1.5,"?/1000000000")	"3/2", "3/2"	#VALUE!, #VALUE!	DIFFERS	Security limit. SheetKit falls back to a bounded fraction search for denominators it cannot use.
TEXT(1.5,"?/99999")	"149999/99999"	"3/9 "	DIFFERS	Raw Excel output recorded as returned. SheetKit applies the fixed denominator.
TEXT(12345678901234567890,"0")	"12345678901234567168"	"12345678901234500000"	DIFFERS	Excel shows 15 significant digits; SheetKit prints the full double value.

Cross-sheet evaluation

Test data: Sheet2!A5 = 1, Sheet2!B5 = =A5+ROW()+COLUMN()*100, Sheet2!C5 = =SUM(A5:B5), Sheet1!A5 = 5.

Behavior	SheetKit	Excel	Status	Notes
=Sheet2!B5 on Sheet1	206	206	MATCH	Unqualified A5, ROW(), and COLUMN() resolve against Sheet2, where the formula lives.
=Sheet2!C5, =SUM(Sheet2!A5:B5) on Sheet1	207, 207	207, 207	MATCH

Deleting rows

Rows 5 and 6 of Sheet1 were deleted (remove_row twice in SheetKit; delete entire row of A5:A6 in Excel). Formulas on Sheet1 and on a second sheet referenced Sheet1.

Behavior	SheetKit	Excel	Status	Notes
Single reference to a deleted cell: =A5, =Sheet1!A5	=#REF!, =Sheet1!#REF!	=#REF!, =Sheet1!#REF!	MATCH
Range partly deleted: SUM(A4:A7), SUM(Sheet1!A6:A9)	SUM(A4:A5), SUM(Sheet1!A5:A7)	same	MATCH	The range shrinks.
Range fully deleted: SUM(A5:A6), SUM(Sheet1!5:5)	SUM(#REF!), SUM(Sheet1!#REF!)	same	MATCH
References below the band: Sheet1!A10, SUM(Sheet1!4:7)	Sheet1!A8, SUM(Sheet1!4:5)	same	MATCH
Whole-column reference: SUM(A:A)	unchanged	unchanged	MATCH
Merged cells C5:D6, E4:E7, F8:G9	removed, E4:E5, F6:G7	same	MATCH
Data validations H5, H8, H3:H7 (identical rules)	removed, H6, H3:H5	one rule on H3:H6	MATCH	The same cells are covered. Excel merges identical rules into one sqref when it saves.
Conditional formats I5:I6, I4:I8	removed, I4:I6	same	MATCH
Hyperlinks on J5, J8	removed, J6	same	MATCH
Comments on L5, L8	removed, L6	same	MATCH
Row page breaks below rows 5 and 8	removed, below row 6	same	MATCH

Inserting rows and columns

After the deletion above, one column was inserted before column A and one row before row 1 (insert_cols and insert_rows in SheetKit; insert on an entire column and an entire row in Excel).

Behavior	SheetKit	Excel	Status	Notes
Whole-column references: SUM(A:A), SUM(Sheet1!B:B), SUM(Sheet1!A:B)	SUM(B:B), SUM(Sheet1!C:C), SUM(Sheet1!B:C)	same	MATCH
Whole-row references: SUM(2:2), SUM(Sheet1!1:1), SUM(Sheet1!4:5)	SUM(3:3), SUM(Sheet1!2:2), SUM(Sheet1!5:6)	same	MATCH	Whole-column and whole-row references shift but are not evaluated. See Known Limitations.
Merges, conditional formats, hyperlinks, comments, page breaks	F5:F6, G7:H8; J5:J7; K7; M7; below row 7	same	MATCH	Data validations cover the same cells; Excel again merges identical rules.

Tables

Table names were set with add_table in SheetKit. In Excel they were set by assigning name on a list object through AppleScript, saving the workbook, and reading the saved name and displayName. The Excel user interface's table name box was not tested.

Behavior	SheetKit	Excel	Status	Notes
Name that differs only in case from an existing table (sales, SALES when Sales exists)	add_table returns an error ("table 'sales' already exists")	Accepted; saved name="sales", displayName="sales_1"	DIFFERS	Deliberate. Excel's object model renames the display name; SheetKit rejects the name instead of renaming silently.
Name that is a cell reference (A1, XFD1048576, R1C1, R, C, RC, R1)	Error ("must not be a cell reference")	A1 saved as displayName="A1_"; R1C1 as "_R1C1"	DIFFERS	Deliberate, as above. XFE1 (beyond the last column) is accepted by both.
Name with a space (Bad Name)	Error ("contains invalid character")	Saved as displayName="Bad_Name"	DIFFERS	Deliberate, as above.
Name starting with a digit (1abc)	Error ("must start with a letter, underscore, or backslash")	Saved as displayName="_1abc"	DIFFERS	Deliberate, as above.
256-character name; 255-character name	Error; accepted	Error -10006 ("Can't set name"); accepted	MATCH
_ok, \back, a.b	Accepted	Accepted	MATCH
Totals row present	TableConfig column with totals_row_function or totals_row_label writes totalsRowCount="1"; the table ref includes the totals row and the autoFilter ref excludes it	totalsRowCount="1", ref="A1:B4", autoFilter ref="A1:B3"	MATCH
SUBTOTAL function numbers for sum, average, count, countNums, min, max, stdDev, var	109, 101, 103, 102, 105, 104, 107, 110	109, 101, 103, 102, 105, 104, 107, 110	MATCH
Accepted totals function names	none, sum, average, count, countNums, min, max, stdDev, var; custom is rejected	The same names plus custom	DIFFERS	Not supported. A custom totals formula needs totalsRowFormula, which TableConfig cannot set. See Known Limitations.
Totals cell formula text	SUBTOTAL(109,[Qty])	Displays =SUBTOTAL(109,[Qty]) in the cell; saves SUBTOTAL(109,Sales[Qty])	MATCH	Excel opens SheetKit's form without repair and calculates it.

Merged cells

Behavior	SheetKit	Excel	Status	Notes
Merging B2:C3 when A1:B2 is already merged	Workbook::merge_cells and StreamWriter::add_merge_cell return a merge overlap error	Accepted; the merge becomes A1:C3	DIFFERS	Deliberate. SheetKit rejects overlapping merges instead of silently enlarging the existing merge.
Merging the same range again (E1:F2 twice)	StreamWriter::add_merge_cell: no-op. Workbook::merge_cells: overlap error	No-op	MATCH (stream), DIFFERS (Workbook)	The Workbook difference is deliberate. Calling merge_cells again on an existing merge is reported rather than ignored.

Comments and shared strings

Behavior	SheetKit	Excel	Status	Notes
Notes list on a sheet with one note and one threaded comment	get_comments returns only the note	Excel comments count is 1 (the note)	MATCH	Excel does not list the [Threaded comment] legacy twin as a note.
Threaded comment content as shown in Excel	get_threaded_comments returns the thread	Not readable	NOT VERIFIABLE	Excel's AppleScript dictionary has no access to threaded comments.
Plain Hello in A1 and bold rich text Hello in A2	Two shared string entries	A1 characters not bold, A2 characters bold	MATCH	The two cells keep separate formatting.

Not Excel-visible

Behavior	SheetKit	Excel	Status	Notes
Deleting the hyperlink on one of two cells that share a relationship	delete_cell_hyperlink removes the relationship only when no remaining hyperlink uses it	n/a	N/A	Package bookkeeping.
New relationship ids	The lowest unused rIdN is used, so gaps are reused	n/a	N/A	Package bookkeeping.
Node.js integer arguments (rows, columns, counts, style ids, outline levels, numeric style and option fields)	Non-finite, fractional, unsafe (beyond Number.MAX_SAFE_INTEGER), and out-of-range values throw "<name> must be an integer from <min> to <max>"	n/a	N/A	API contract. Earlier releases let napi truncate, wrap, or turn NaN into 0.

Summary

Of the 74 rows above, 54 MATCH, 14 DIFFER, 1 is split (merging the same range again matches for StreamWriter and differs for Workbook), 2 are NOT VERIFIABLE, and 3 are N/A.

• Security limits: the TEXT format code rows. SheetKit keeps formatting bounded instead of rejecting format codes Excel rejects.
• Deliberate: table naming (reject instead of rename) and merges (reject overlaps instead of enlarging).
• Not reproduced: Excel's clamping of out-of-range DATE day arguments, Excel's 15-digit display precision in TEXT, and floating-point error in ROUND near 1E308.