What is the OXT file format?
.oxt files are associated with LibreOffice and Apache OpenOffice productivity suites.
What kind of data do OXT files store?
.oxt files are used for distributing extensions (plugins) for LibreOffice and Apache OpenOffice. Each package is a ZIP archive containing UNO components, Basic or Python scripts, configuration XML, and icon files. A required META-INF/manifest.xml lists all items in the archive, while description.xml carries the extension's display name, version, and minimum office-suite version requirement.
OXT extensions can add such functionalities as:
- advanced spell checking and grammar tools,
- syntax highlighting for programming languages,
- automatic image processing in Draw,
- additional export filters and file formats,
- access to online template and content databases.
Both LibreOffice and Apache OpenOffice are free, open-source software. Users are free to create their own .oxt plugins and share them with other users.
How to install an OXT plugin?
.oxt files can be installed using the built-in Extension Manager (Tools → Extension Manager → Add). Newer versions of the suite install an extension automatically by double-clicking the .oxt file. Extensions can also be applied to selected components rather than globally, and the command-line tool unopkg provides a scripted installation option.
Security & safety
RISK: MEDIUMOXT extensions can contain compiled code (UNO shared libraries), Basic macros, and Python scripts that execute with LibreOffice's privileges. Install extensions only from the official LibreOffice Extension Center (extensions.libreoffice.org) or from trusted developers. Extensions are NOT sandboxed - a malicious OXT can access the file system, network, and execute OS commands via macros. LibreOffice shows a confirmation dialog and (for low-trust sources) a macro security warning during installation.
Format details
in a nutshellPrograms that open OXT files
Windows3 apps
LibreOffice
Open-source Tools → Extension Manager → Add → select the .oxt file → confirm installation; restart LibreOffice when prompted. 
7-Zip
Open-source Right-click the .oxt → Open archive - inspect contents without installing (it's a ZIP). 
macOS3 apps
Linux2 apps
LibreOffice
Open-source Tools → Extension Manager → Add; or command line: unopkg add yourextension.oxt Technical details
deep spec| Container format | ZIP archive (PK magic bytes 50 4B 03 04 at offset 0) |
| Compression | DEFLATE per-entry (standard ZIP compression) |
| Byte order | Little-endian (ZIP structures) |
| Required internal files | META-INF/manifest.xml (item registry with media types) and description.xml (extension ID, version, dependencies) |
| Scripting languages | UNO Basic, Python, Java (via UNO component model) |
| MIME type | application/vnd.openofficeorg.extension |
| Maximum archive entries | 65,535 (ZIP format limit) |
| CLI installation tool | unopkg (bundled with LibreOffice/OpenOffice) - supports add, remove, list, and reinstall operations |
| Typical file size | 10 KB - 50 MB (most extensions fall in the 50 KB - 5 MB range) |
| Cross-compatibility | LibreOffice and Apache OpenOffice share the format but are NOT always API-compatible; extensions may target one suite only |
| Inspection method | Rename .oxt to .zip and open with any ZIP tool to examine the internal structure |
| Encoding | Binary container (ZIP) with XML and script text content inside |
| Released | 2005 (OpenOffice.org 2.0) |
| Latest version | N/A (container format; individual extensions versioned independently) |
| Open standard | Yes · royalty-free |
| Specification | wiki.openoffice.org |
OXT conversions
Community Q&A
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