What is the OTS file format?
OTS (OpenDocument Spreadsheet Template) is a template file format used by spreadsheet applications such as LibreOffice Calc and Apache OpenOffice Calc. Many other spreadsheet programs also support this format. The format specification is based on XML as defined by the OASIS OpenDocument (ODF) standard. Technically, an .ots file is a ZIP archive containing XML files - structurally identical to an .ods spreadsheet file but flagged as a template by its internal mimetype entry. By default, opening a template from the file manager creates a new unnamed spreadsheet based on the template, leaving the original .ots file untouched.
Templates and their usage
An .ots file can serve as a base for generating any number of new .ods spreadsheet files with predefined styles and formatting. Besides formatting settings, a template file can define default layouts for document types such as shipping manifests or accounting worksheets. Users can also download community-created templates for popular document types. To edit the template directly, renaming it from .ots to .ods allows modification in any compatible application.
Security & safety
RISK: MEDIUMOTS files can contain macros (Basic scripts) which execute on open - same risk as .ods macro files. LibreOffice and OpenOffice prompt before running macros. Disable macros in settings if the source is untrusted. No known exploits specific to the template format itself.
Format details
in a nutshellPrograms that open OTS files
Windows4 apps
Microsoft Excel
Paid File > Open, select the .ots file. Excel treats it as a template and opens a new workbook. 
LibreOffice Calc
Open-source Double-click opens a new document from the template. To edit the template: Tools > Macros or File > Templates > Edit Template. 
ONLYOFFICE Desktop Editors
Open-source Open directly; ONLYOFFICE renders ODF templates with good fidelity. 
macOS2 apps
Linux2 apps
Google Sheets
Free Upload .ots to Google Drive, then open with Google Sheets. Converts to Google Sheets format. Technical details
deep spec| File type | ZIP-based XML package (ODF container format) |
| MIME type | application/vnd.oasis.opendocument.spreadsheet-template |
| Magic bytes | 50 4B 03 04 ("PK") - standard ZIP local file header signature at offset 0 |
| Encoding | UTF-8 (XML content files within ZIP); ZIP header fields are little-endian |
| Compression | DEFLATE (per ZIP entry); mimetype entry stored uncompressed as required by ODF |
| Encryption | Optional AES-256 (ODF 1.2+); Blowfish used in older ODF versions |
| Typical size | 5 KB - 2 MB (templates are usually small; grows with embedded images or many defined styles) |
| ODF standard | ODF 1.3 (OASIS, 2021); ISO/IEC 26300:2006 and subsequent revisions |
| Key ZIP entries | mimetype, content.xml (cells and formulas), styles.xml, meta.xml, settings.xml, Thumbnails/, manifest.xml |
| Digital signature | Optional XML digital signatures supported in ODF 1.2+, stored as documentsignatures.xml inside the ZIP |
| Open-on behavior | Opening creates a new unnamed .ods document; the .ots template file is never modified |
| Edit-template method | Rename .ots to .ods to open and modify the template file directly in any compatible application |
| Max ZIP entries | 65,535 (ZIP specification limit); ODF adds no further restriction |
| OS support | Windows, Linux, macOS, Android, iOS |
| Released | 2005 (ODF 1.0, OASIS); ISO/IEC 26300 since 2006 |
| Latest version | ODF 1.3 (OASIS standard, 2021) |
| Open standard | Yes · royalty-free |
| Specification | www.oasis-open.org |
OTS conversions
Community Q&A
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