Supported Formats

Spreadsheet formats

Format	Extension	Read	Write	Notes
Excel Workbook	.xlsx	✔	✔	The primary and best-supported format
Excel Macro-Enabled Workbook	.xlsm	✔	✔	VBA preserved, never executed
Excel Binary Workbook	.xlsb	✔	✔	Binary OOXML; faster and smaller than .xlsx
Excel 97–2003	.xls	✔	✔	BIFF8. Subject to the format’s own limits — 65,536 rows, 256 columns
OpenDocument Spreadsheet	.ods	✔	✔	Formulas and values; including encrypted ODS. 0.1.0 builds wrote and read values only
Comma-Separated Values	.csv	✔	✔	One sheet of values; type sniffing on import. Text is exported as is — see Import and Export
JSON	.json	✔	✔	One sheet as an array of row objects keyed by the header row; values only

Workbook.open(Path) also reads the template variants .xltx and .xltm, tab-separated .tsv and .txt, .html/.htm tables, .ots, .sxc, and flat .fods, and SpreadsheetML 2003 .xml.

Output formats

Format	Write	Notes
PDF	✔	Paginated; encryption, permissions, watermarks, bookmarks, PDF/A
PNG	✔	Per sheet or per page
SVG	✔	Vector glyph outlines; text is not selectable or searchable
JPEG, GIF, BMP, TIFF	✔	Per sheet or per page
HTML	✔	Styled table, single-file or with attachments

See Rendering.

Feature support

Beyond values and formulas, these are modelled — read, computed where applicable, written, and rendered:

Formulas	500+ functions, dynamic arrays and spill, structured references, iterative calculation, shared formulas, external references with cached values
Number formats	Full Excel format-code syntax, including conditional sections and locale-aware formatting
Styles	Fonts, fills (solid, patterned, gradient), borders, alignment, rotation, indent, themes, named styles, indexed and theme colours
Charts	20+ types, series, axes, data labels, error bars, trendlines, 3-D views, chart sheets. Map charts are read and written but currently render as a placeholder frame.
Pivot tables	Field layout, aggregation, all four filter kinds, sorting, date and numeric grouping, show-values-as, calculated fields and items, slicers, timelines
Tables	Header and totals rows, banding, styles, auto-expansion, structured references
Conditional formats	All rule kinds, colour scales, data bars, icon sets
Validation	All types, input and error messages, dropdowns
Comments	Legacy notes and modern threaded comments
Drawings	Pictures, shapes, connectors, SmartArt, WordArt, 3-D effects, shadows
Sparklines	Line, column, and win/loss groups
Form controls	Ten control types with linked cells
Protection	Sheet, range, workbook structure, write protection
Security	ECMA-376 agile encryption, ODS encryption, OPC digital signatures
Page setup	Print areas, titles, margins, scaling, fit-to-page, headers and footers, page breaks, watermarks
Sheet types	Worksheets, chart sheets, dialog sheets, macro sheets

These are preserved verbatim — carried through a round trip, but not interpreted:

• VBA projects and macro modules
• ActiveX controls and OLE embeddings
• Custom XML parts
• Unknown extension lists (extLst), including features newer than the build
• Drawing parts the model does not interpret

Known limits

Worth knowing before you design around them:

• .xls is bounded by BIFF8. 65,536 rows and 256 columns, and no feature introduced after Excel 2003. Saving a larger or more modern workbook to .xls loses what does not fit. Prefer .xlsx or .xlsb.
• CSV is one sheet of text. No formulas, styles, or objects survive it.
• Macros are never executed. A .xlsm round-trips with its VBA intact, but nothing in it runs.
• A round trip is not byte-identical. Modelled parts are rewritten. Do not compare checksums.
• Rendering depends on fonts. A missing font falls back to a metric-compatible substitute, which changes line breaks. Ship the fonts you need — see Rendering.
• XPS output is not available. Use PDF for paginated output.
• Formula function coverage is per build. Functions.list() is the authoritative answer for the version you have, not any list in documentation.