LibreOffice OXT Extension Packaging Standards

LibreOffice extensions use the OpenOffice.org Extension (.oxt) format to distribute add-ons, templates, dictionaries, and custom functionality. An .oxt package is essentially a standard ZIP archive containing metadata, configuration files, and program code organized according to the Universal Network Objects (UNO) package specification. This structure allows LibreOffice’s Extension Manager to install, update, and manage third-party enhancements safely and consistently across different operating systems.

The Archive Format

At the binary level, an .oxt file follows the standard PKZIP 2.04g specification. Developers can create or inspect these files using any standard ZIP utility by simply appending or changing the file extension to .oxt.

Core Descriptor Files

Every valid .oxt package requires specific XML files to declare its contents, dependencies, and metadata:

• META-INF/manifest.xml: The package manifest is the foundational descriptor required by LibreOffice. It registers all files within the archive with their corresponding media types, telling the application how to process each component (such as UNO components, configuration data, or dialog libraries).
• description.xml: Located in the root directory, this file provides user-facing metadata, including the extension’s unique identifier, display name, publisher details, version number, localized descriptions, and minimal LibreOffice version compatibility requirements.

Supported Component Technologies

The .oxt standard supports several programming languages and asset types, declared via the manifest.xml file using specific media types:

• LibreOffice Basic: Encapsulated in XML-based script libraries.
• Python: Scripts and modules utilizing the LibreOffice Python-UNO bridge.
• Java: Compiled JAR files implementing UNO interfaces.
• C++: Precompiled shared libraries (.dll, .so, .dylib) built against the LibreOffice Software Development Kit (SDK).
• Dictionaries and Language Packs: Hunspell spelling files, hyphenation rules, and thesaurus data configured via dictionary list files.

Configuration Integration

Extensions modify the LibreOffice user interface and behavior using XML Configuration Update (.xcu) and XML Configuration Schema (.xcs) files. These files declare custom menus, toolbars, shortcuts, status bar controls, and application settings directly into LibreOffice’s internal configuration registry upon installation.