Exhaustive capability matrix — every feature either library supports, compared side-by-side.

Legend	Meaning
✅	Fully supported
⭐	Supported + superior implementation
🔒	SheetJS Pro only (paid license)
❌	Not supported
🚧	Partial / limited support

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modern-xlsx	SheetJS
Categories won	20	8
Ties	4
Total features	250	173

modern-xlsx wins: Workbook ops, merge cells, styling (free), frozen panes, data validation, conditional formatting, hyperlinks, comments, named ranges, page setup, sheet protection, date utilities, rich text, images, barcodes, table layout, validation/repair, web workers, performance, API design

SheetJS wins: Read formats (18 vs 1), write formats (20 vs 1), I/O ops, document properties, cell ref utils, number formatting, sheet conversion, streaming

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Format	modern-xlsx	SheetJS	Notes
XLSX (Office Open XML)	✅	✅	Both full support
XLSM (Macro-enabled)	❌	✅	Data only, no macros
XLSB (Binary)	❌	✅
XLS (BIFF8/5/4/3/2)	❌	✅	Legacy Excel 97-2003
XLML (SpreadsheetML 2003)	❌	✅
ODS (OpenDocument)	❌	✅
FODS (Flat ODS)	❌	✅
CSV	❌	✅
TSV / TXT	❌	✅
HTML tables	❌	✅
SYLK	❌	✅
DIF	❌	✅
PRN	❌	✅
ETH (EtherCalc)	❌	✅
DBF (dBASE)	❌	✅
WK1/WK3/WKS (Lotus)	❌	✅
QPW (Quattro Pro)	❌	✅
Numbers (Apple)	❌	✅	Requires numbers option

Format	modern-xlsx	SheetJS	Notes
XLSX	⭐	✅	modern-xlsx: 8x smaller output
XLSM	❌	✅
XLSB	❌	✅
XLS (BIFF8/5)	❌	✅
XLS (BIFF4/3/2)	❌	✅
XLML	❌	✅
ODS / FODS	❌	✅
CSV	❌	✅	modern-xlsx: string only via sheetToCsv
HTML	❌	✅	modern-xlsx: string only via sheetToHtml
Others (SYLK, DIF, RTF, etc.)	❌	✅	10+ additional legacy formats

Feature	modern-xlsx	SheetJS	Notes
Read from buffer	✅	✅
Read from file	✅	✅
Read sync	❌	✅	modern-xlsx: async-only (WASM)
Write to buffer	✅	✅
Write to file	✅	✅
Write sync	❌	✅
Write to Blob (browser)	⭐	✅	Native WASM Blob
Parse CFB / ZIP	❌	✅
Custom FS / codepage	❌	✅
WASM init	⭐	❌

Feature	modern-xlsx	SheetJS
Create / get / add / remove sheets	✅	✅ (no remove)
Sheet visibility	❌	✅
Date system	✅	✅
Workbook views	⭐	🚧
Document properties	⭐	🚧
Serialize to JSON	✅	❌
Validate workbook	⭐	❌
Repair workbook	⭐	❌

Feature	modern-xlsx	SheetJS	Notes
Strings, numbers, booleans	✅	✅
Error values	✅	✅
Date values (native type)	❌	✅	SheetJS type "d"
Stub/empty cells	❌	✅	SheetJS type "z"
Inline strings	✅	❌
Formula strings (type)	✅	❌
Style index	⭐	🔒	modern-xlsx free
Number format override	🚧	✅	SheetJS: per-cell .z

Feature	modern-xlsx	SheetJS	Notes
Style builder (fluent API)	⭐	❌
Font (name, size, bold, italic, color, underline, strike)	⭐	🔒	Free vs paid
Fill (solid, 18 patterns, gradient)	⭐	🔒
Border (4 sides + diagonal, 13 styles, colors)	⭐	🔒
Alignment (H/V, wrap, rotation, indent, shrink)	⭐	🔒
Cell protection (locked/hidden)	⭐	🔒
Number format (custom/built-in)	⭐	✅	Community has per-cell .z
DXF / Cell styles / CellXf / Theme colors	⭐	❌

Feature	modern-xlsx	SheetJS
All validation types (list, whole, decimal, date, time, textLength, custom)	⭐	🔒
Input prompts and error alerts	⭐	🔒
Color scales / data bars / icon sets	⭐	🔒
DXF style references / CFVO	⭐	🔒

Feature	modern-xlsx	SheetJS
Add/remove hyperlinks with tooltip	✅	✅ (no tooltip, no remove)
Add/remove comments	✅	✅ (no remove)
Full CRUD named ranges	✅	🚧 (read-only)

Feature	modern-xlsx	SheetJS
Orientation, paper size, fit-to, scale	✅	❌
Page margins	✅	✅
Sheet protection (14 granular fields)	⭐	🚧
Frozen panes	✅	✅
Auto filter + filter columns	⭐	✅

Feature	modern-xlsx	SheetJS
Column ↔ letter, cell encode/decode, range encode/decode	✅	✅
Encode/decode row, split cell ref	❌	✅
Date ↔ serial, Temporal-like input	⭐	❌
Parse date code	❌	✅

Feature	modern-xlsx	SheetJS
AoA/JSON → sheet, sheet → JSON/CSV/HTML	✅	✅
Add AoA/JSON to existing sheet	✅	✅
Sheet → TXT / formulae / row objects	❌	✅
DOM table → sheet/book	❌	✅

Feature	modern-xlsx	SheetJS
Stream to JSON/CSV/HTML/XLML	❌	✅
WASM streaming reader (SAX)	⭐	❌
Parallel sheet parsing (rayon)	⭐	❌

Feature	modern-xlsx	SheetJS
RichTextBuilder (bold, italic, colored, styled)	⭐	❌
Image embedding (PNG/JPEG/GIF)	⭐	🔒
Charts (create)	❌	🔒

Feature	modern-xlsx	SheetJS
9 barcode types + PNG renderer + XLSX embed	⭐	❌
Table layout engine (drawTable/drawTableFromData)	⭐	❌
Workbook validation & repair	⭐	❌
Web Worker support	⭐	❌

Benchmark	modern-xlsx	SheetJS	Ratio
Read 10K rows	faster	baseline	~4.6x
Write 10K rows	faster	baseline	~1.3x
Output file size	smaller	baseline	~8x
aoaToSheet 50K rows	faster	baseline	~2x
sheetToJson 10K rows	faster	baseline	~2x
sheetToCsv 10K rows	faster	baseline	~2.4x
Bundle size	~300KB (WASM)	~200KB (JS)	1.5x larger
Zero runtime deps	✅	❌
TypeScript types	109+ types	basic
Multi-threading	rayon flag	❌

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See the full comparison with 250 features in docs/FEATURE-COMPARISON.md