Most projects just need XLSX. A focused library keeps the bundle and workbook API small while leaving file-system I/O to the host application.
xlsx-format does one thing well: read and write modern Excel files. The result is a library you can actually tree-shake, await, and ship to the browser without a separate bundle.
Comparison
| xlsx-format 2.4.2 | SheetJS 0.18.12 | ExcelJS 4.4.0 |
|---|
| Written in | TypeScript (strict) | JavaScript with typings | JavaScript with TypeScript types |
| Async | Promise-based API | Synchronous public API | Promise-based selected APIs |
| Module format | ESM + CJS | ESM + CJS | CJS + browser build |
| Tree-shakeable | Yes | Limited | Limited |
| Browser support | Yes (read / write) | Yes (separate bundle) | Yes (exceljs.browser.js) |
| Formats | XLSX / XLSM¹ / CSV / TSV / HTML | Many spreadsheet formats | XLSX / CSV |
| Styled reports | Yes | Yes | Yes |
| API style | Named exports | Namespace object | Class-based |
| License | Apache 2.0 | Apache 2.0 | MIT |
The version labels identify the snapshots used for this orientation table. The SheetJS package metadata advertises ESM/CJS entry points and browser bundles. ExcelJS documents its browser build and workbook API in its browser documentation.
Feature Support
¹ XLSM support covers workbook cell data and macro-free output containers. VBA projects are not read, preserved, or written. Do not use an XLSM read/write round trip when macros must survive unchanged.
What xlsx-format can read from and write to XLSX files at a glance.
Cell Data
| Feature | Read | Write | Notes |
|---|
| Strings | Yes | Yes | Via shared string table or inline |
| Numbers | Yes | Yes | Full floating-point precision |
| Booleans | Yes | Yes | Native boolean cell type |
| Dates | Yes | Yes | Serial numbers or ISO 8601 (cellDates option) |
| Error values | Yes | Yes | #NULL!, #DIV/0!, #VALUE!, etc. |
| Feature | Read | Write | Notes |
|---|
| Cell formulas | Yes | Yes | Stored in cell.f |
| Array formulas | Yes | Yes | Range reference in cell.F, dynamic array flag cell.D |
| Shared formulas | Yes | -- | Expanded to individual cell formulas on read |
| Feature | Read | Write | Notes |
|---|
| Built-in formats | Yes | Yes | 164+ standard Excel format codes |
| Custom formats | Yes | Yes | e.g. #,##0.00, yyyy-mm-dd, custom patterns |
| Format display text | Yes | Yes | Formatted value in cell.w via full SSF engine |
Styles
| Feature | Read | Write | Notes |
|---|
| Rich text (bold, italic, underline, color) | Yes | Yes | Preserved in shared strings |
| Cell number format references | Yes | Yes | Style index maps to format codes |
| Cell fonts | Yes | Yes | Name, size, bold, and RGB/ARGB color |
| Solid fills | Yes | Yes | Foreground color for title rows, headers, and totals |
| Borders | Yes | Yes | Top, right, bottom, left with thin or medium |
| Alignment | Yes | Yes | Horizontal, vertical, and wrap text |
| Feature | Read | Write | Notes |
|---|
| Legacy comments | Yes | Yes | ECMA-376 format with VML positioning |
| Threaded comments | Yes | Yes | Modern reply-chain format |
| Comment authors | Yes | Yes | Author list and people mapping |
Hyperlinks
| Feature | Read | Write | Notes |
|---|
| External URLs | Yes | -- | Parsed from relationships |
| Internal links | Yes | -- | #Sheet2!A1 syntax |
| Tooltips | Yes | -- | Stored in cell.l.Tooltip |
Sheet Structure
| Feature | Read | Write | Notes |
|---|
| Multiple sheets | Yes | Yes | Ordered sheet list with unique names |
| Merge regions | Yes | Yes | Rectangular merge ranges |
| Column widths | Yes | Yes | Character-unit widths |
| Row heights | Yes | Yes | Point-based heights |
| Hidden columns / rows | Yes | Yes | Via hidden flag |
| Frozen panes | Yes | Yes | Top rows and/or left columns via !views |
| Auto-filter range | Yes | Yes | Filter range definition (no filter criteria) |
| Page margins | Yes | Yes | Left, right, top, bottom, header, footer |
| Feature | Read | Write | Notes |
|---|
| Sheet visibility | Yes | Yes | Visible, hidden, very hidden |
| Defined names | Yes | Yes | Workbook-scoped and sheet-scoped |
| Document properties | Yes | Yes | Title, author, dates, keywords, etc. |
| Custom properties | Yes | Yes | User-defined key/value pairs |
| Date system (1904 mode) | Yes | Yes | Mac Excel legacy support |
| Dynamic array metadata | Yes | Yes | XLDAPR spill-range support |
| Feature | Read | Write | Notes |
|---|
| JSON objects | Yes | Yes | sheetToJson / jsonToSheet |
| Arrays of arrays | Yes | Yes | sheetToJson({ header: 1 }) / arrayToSheet |
| CSV | Yes | Yes | csvToSheet / sheetToCsv |
| TSV | Yes | Yes | Via separator option |
| HTML tables | Yes | Yes | htmlToSheet / sheetToHtml |
Not Yet Supported
Conditional formatting, data validation, charts, images, pivot tables, sparklines, VBA macros, custom theme XML, calculation-chain exposure, raw ZIP entry exposure, digital signatures, sheet/workbook protection, outline grouping.
