What is the OTT file format?
Files with the .ott extension store text document templates saved in the OpenDocument standard. Internally, an .ott file is a ZIP archive containing a set of XML files - the same structure used by .odt documents, but identified as a template by a mimetype entry that reads application/vnd.oasis.opendocument.text-template.
Unlike regular documents, templates are designed as reusable starting points rather than finished files. They primarily define:
- Page layout,
- Default styles,
- Fonts,
- Formatting.
.ott stands for OpenDocument Text Template and applies specifically to text documents - spreadsheets and presentations use their own template formats (.ots and .otp respectively). Opening an .ott file in LibreOffice Writer or Apache OpenOffice creates a new, untitled .odt document based on it; to edit the template itself, you must open it explicitly through the application's template manager.
Templates can be created from existing documents using word processors that support the OASIS OpenDocument standard, such as LibreOffice Writer or Apache OpenOffice Writer. They are typically used to generate:
- Standardized business documents,
- Newsletters,
- Business notes,
- Official documents.
Many applications offer built-in template libraries, and numerous websites provide .ott templates for free download.
Security & safety
RISK: LOWOTT templates are ordinary ODF files and generally safe, with the same caveat as all office documents: they can carry macros (LibreOffice Basic) and templates are a natural place to hide auto-running code, which both LibreOffice and Word block or prompt about by default - never enable macros in a template you didn't expect. Embedded hyperlinks and OLE objects can point to malicious destinations. Opening an OTT with macros disabled is safe; as a ZIP, you can rename it to .zip and inspect the contents before trusting it.
Format details
in a nutshellPrograms that open OTT files
Windows4 apps
Microsoft Word
Paid File - Open the .ott (ODF supported since Word 2007). To make it a Word template, Save As .dotx. Complex ODF styling may shift slightly. 
LibreOffice Writer
Open-source Double-click to start a new document from the template, or File - Templates - Manage Templates to edit the OTT itself. Native, full-fidelity. 
ONLYOFFICE Desktop Editors
Open-source Free suite; opens the OTT, edits, and saves to ODT/DOCX or as a template.
Apache OpenOffice Writer
Open-source Opens OTT natively (still ODF 1.2); sparsely maintained - LibreOffice is the actively developed choice. 
macOS2 apps
LibreOffice Writer
Open-source Native OTT support; free for Apple silicon and Intel. New-from-template on double-click. 
Microsoft Word for Mac
Paid Opens OTT like the Windows version. (Apple Pages imports ODF with some formatting loss.) 
Linux2 apps
LibreOffice Writer
Open-source Preinstalled on most desktops; double-click for a new document, or manage templates to edit the OTT.
Collabora Office / ONLYOFFICE
Open-source LibreOffice-based suites; open and edit OTT with desktop-grade fidelity. 
Android1 app
Google Docs
Free Upload the .ott to Google Drive and open - it converts to a Docs document; download back as .odt or .docx. Technical details
deep spec| Container | ZIP archive (physically identical to a `.zip` file) |
| MIME type | `application/vnd.oasis.opendocument.text-template` |
| Magic bytes | `50 4B 03 04` (PK header at offset 0); uncompressed `mimetype` entry near offset 38 contains `application/vnd.oasis.opendocument.text-template`, distinguishing it from `.odt` |
| Internal XML encoding | UTF-8 (used in `content.xml`, `styles.xml`, `meta.xml`, `settings.xml`) |
| Compression | DEFLATE per entry; the leading `mimetype` file is stored uncompressed (ZIP STORED method) so it is readable without decompression |
| Encryption | Optional AES-256 password protection applied per stream; encryption metadata recorded in `META-INF/manifest.xml` |
| Typical file size | 8 KB - 2 MB; increases when images or embedded fonts are included |
| Internal structure | `mimetype`, `content.xml`, `styles.xml`, `meta.xml`, `settings.xml`, `META-INF/manifest.xml`, `Pictures/` - layout identical to `.odt` |
| Template vs. document distinction | The sole structural difference from `.odt` is the `mimetype` entry value; ODF version is recorded in the `office:version` attribute (e.g., `1.3`) in `content.xml` and `styles.xml` |
| Template open behaviour | Opening in LibreOffice Writer spawns a new untitled `.odt`; editing the template itself requires the explicit 'Edit Template' workflow or opening via the template manager |
| Integrity checking | ZIP CRC-32 checksum per entry; optional XML digital signatures stored in `META-INF/` |
| Flat-file equivalent | `.fodt` - a single uncompressed XML file serving the same template role without ZIP packaging |
| Standard body | OASIS Open Document Format TC; also published as ISO/IEC 26300 |
| Platform support | Windows, macOS, Linux, Android, iOS, and browser-based environments (Google Docs, ONLYOFFICE Online) |
| Released | 2005 (ODF 1.0, OASIS); ISO/IEC 26300 since 2006; current major version ODF 1.3 (2021) |
| Latest version | ODF 1.3 (OASIS standard, 2021) |
| Open standard | Yes · royalty-free |
| Specification | www.oasis-open.org |
OTT conversions
Community Q&A
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