What is the SXC file format?
Files with .sxc extension store spreadsheet documents created with StarOffice or OpenOffice.org 1.x. .sxc files support standard spreadsheet capabilities, including:
- charts
- formulas
- functions
- macros
.sxc was the native spreadsheet standard for OpenOffice.org through version 1.1, although it has since been replaced by the more widely adopted .ods (OpenDocument Spreadsheet), which became the default in OpenOffice.org 2.0 in 2005.
.sxc belongs to the OpenOffice.org XML format family developed by Sun Microsystems. Introduced in 2002 with StarOffice 6.0 and OpenOffice.org 1.0, the format packages all spreadsheet data inside a ZIP archive containing several XML files: content.xml (sheet data and formulas), styles.xml, meta.xml, and settings.xml, plus a META-INF/manifest.xml inventory. The first ZIP entry is an uncompressed mimetype file holding the string application/vnd.sun.xml.calc. This plaintext marker lets tools identify the file without full decompression and distinguishes .sxc from .ods, whose mimetype reads application/vnd.oasis.opendocument.spreadsheet. The current OpenDocument standard (ISO/IEC 26300:2006) took many inspirations from this earlier OpenOffice.org XML design.
Although .sxc is no longer commonly used due to the wider adoption of open formats, many programs still support this format. LibreOffice Calc opens and converts .sxc files natively to formats including .ods or .xlsx without data loss. Apache OpenOffice Calc retains similar read support. Modern Microsoft Excel cannot open .sxc directly.
Security & safety
RISK: LOWAn SXC is a data document and, like all office ZIP+XML formats, can in principle contain macros (StarBasic), which LibreOffice/OpenOffice block or prompt about by default - never enable macros in a spreadsheet you didn't expect. Given the format's age, most SXC files in the wild are plain legacy data and are harmless to open with macros disabled. The bigger practical risk is bit-rot: convert important SXC files to ODS/XLSX so they remain openable.
Format details
in a nutshellPrograms that open SXC files
Windows2 apps
LibreOffice Calc
Open-source File > Open the .sxc - LibreOffice imports the legacy format; re-save as .ods or .xlsx. The recommended opener. 
Apache OpenOffice Calc
Open-source Opens .sxc natively (it was OpenOffice's own old format), but the project is only sporadically maintained - LibreOffice is preferred. 
macOS2 apps
LibreOffice Calc
Open-source Free for Apple silicon and Intel; opens .sxc and exports to ODS/XLSX/CSV/PDF.
Apache OpenOffice Calc
Open-source Opens the legacy .sxc; lightly maintained - prefer LibreOffice on modern macOS. 
Linux1 app
LibreOffice Calc
Open-source Preinstalled on most desktops; double-click the .sxc to open, then Save As ODS/XLSX.
CloudConvert
Freemium Upload the .sxc and convert to xlsx/ods/csv/pdf in the browser (uses a LibreOffice backend) - no install. Technical details
deep spec| Container format | ZIP archive (compatible with standard zip tools) |
| Internal content encoding | UTF-8 XML |
| Compression | DEFLATE per ZIP entry; the leading mimetype entry is stored uncompressed (ZIP STORED method) |
| MIME type | application/vnd.sun.xml.calc |
| Magic bytes | 50 4B 03 04 (PK) at offset 0; uncompressed mimetype entry near offset 38 contains the literal string application/vnd.sun.xml.calc |
| Primary XML file | content.xml - holds all sheet data, cell values, formulas, and named ranges |
| Manifest | META-INF/manifest.xml lists every archive entry with its MIME type |
| Integrity check | Per-entry ZIP CRC-32 |
| Template variant | .stc (StarOffice Calc Template) uses the same ZIP/XML structure with MIME type application/vnd.sun.xml.calc.template |
| Byte order | Little-endian (ZIP binary structures) |
| Macro language | StarBasic (OOo Basic) macros stored in XML within the archive |
| Predecessor format | Binary StarCalc format (.sdc) used in StarOffice 5.x and earlier |
| Successor format | ODF Spreadsheet (.ods, ISO/IEC 26300), default from OpenOffice.org 2.0 (2005) |
| Sheet features | Multiple sheets, named cell ranges, charts, formulas, conditional formatting |
| Platform origin | Windows, macOS, Linux, Solaris - all platforms where StarOffice/OpenOffice.org 1.x was distributed |
| Released | 2002 (StarOffice 6.0 / OpenOffice.org 1.0); native through OOo 1.1 |
| Latest version | OpenOffice.org XML 1.x (final in OOo 1.1, 2003); superseded by ODF/ODS in OOo 2.0 (2005) |
| Open standard | Yes · royalty-free |
| Specification | www.openoffice.org |
SXC conversions
Community Q&A
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