---
title: SSF Number Formatter
---

As explained in ["Number Formats"](/docs/csf/features/nf), modern spreadsheet
file formats separate "content" from "presentation". Instead of storing a
formatted value like `$3.50`, applications will store the underlying value
(`3.50`) and the number format (`$0.00`). Parsers are expected to render values.

The SheetJS `SSF` ("SpreadSheet Formatter") library formats numbers according
to the number formatting rules defined in Excel and other spreadsheet software[^1]

A version of the library ships with the main file processing library. It is
deeply integrated in SheetJS CE API functions including `read`[^2], `write`[^3],
and `sheet_to_json`[^4].

The library is also available for standalone use on the SheetJS CDN[^5].

The source code and project documentation is hosted on the SheetJS git server at
<https://git.sheetjs.com/sheetjs/sheetjs/src/branch/master/packages/ssf>

[^1]: The number formatting rules are sketched in ECMA-376. A rough grammar is defined in the MS-XLS specification.
[^2]: See [`read` in "Reading Files"](/docs/api/parse-options)
[^3]: See [`write` in "Writing Files"](/docs/api/write-options)
[^4]: See [`sheet_to_json` in "Utilities"](/docs/api/utilities/array#array-output)
[^5]: See <https://cdn.sheetjs.com/ssf/> for more details.