Implementation:SeleniumHQ Selenium ClasspathExtension

Knowledge Sources	SeleniumHQ_Selenium Selenium Documentation
Domains	WebDriver, Firefox_Browser
Last Updated	2026-02-12 00:00 GMT

Overview

ClasspathExtension implements the Extension interface to load and install Firefox browser extensions from the Java classpath into a Firefox profile.

Description

The ClasspathExtension class enables loading Firefox extensions (XPI files) that are bundled as resources within the Java classpath. It takes a reference class (used to locate resources via Class.getResourceAsStream()) and a resource path string. When writeTo() is called, it verifies the resource is a zipped file (XPI format), creates a staging directory within the target extensions directory, extracts the classpath resource to that staging area, and then delegates to FileExtension to perform the final installation. This class only supports zipped (XPI) extensions and will throw a WebDriverException if the resource is not in ZIP format.

Usage

Use ClasspathExtension when you need to install a Firefox extension that is packaged as a resource within your project's classpath (e.g., bundled in a JAR file). This is typically invoked indirectly through FirefoxProfile.addExtension(Class, String) when the specified path does not correspond to an existing file on disk.

Code Reference

Source Location

• Repository: SeleniumHQ_Selenium
• File: java/src/org/openqa/selenium/firefox/ClasspathExtension.java

Signature

public class ClasspathExtension implements Extension {

    public ClasspathExtension(Class<?> loadResourcesUsing, String loadFrom)

    @Override
    public void writeTo(File extensionsDir) throws IOException
}

Import

import org.openqa.selenium.firefox.ClasspathExtension;

I/O Contract

Constructor Parameters

Parameter	Type	Description
loadResourcesUsing	Class<?>	The class whose classloader is used to locate the extension resource via getResourceAsStream().
loadFrom	String	The classpath resource path to the extension file (must be a zipped/XPI file).

Methods

Method	Input	Output	Description
writeTo	File extensionsDir	void	Extracts the classpath extension resource to a staging directory and installs it into the given extensions directory via FileExtension.

Exceptions

Exception	Condition
WebDriverException	The resource at loadFrom is not a zipped file.
IOException	An I/O error occurs while creating directories or writing the extension file.
IllegalArgumentException	The resource specified by loadFrom cannot be found on the classpath of the given class.

Usage Examples

// Add a classpath extension to a Firefox profile
FirefoxProfile profile = new FirefoxProfile();
profile.addExtension(MyTestClass.class, "/extensions/my-extension.xpi");

FirefoxOptions options = new FirefoxOptions();
options.setProfile(profile);
WebDriver driver = new FirefoxDriver(options);

// Direct usage of ClasspathExtension
ClasspathExtension extension = new ClasspathExtension(
    MyTestClass.class, "/extensions/my-extension.xpi");
extension.writeTo(new File("/path/to/profile/extensions"));

Related Pages

• FirefoxProfile - Manages extensions and calls ClasspathExtension when loading from classpath
• HasExtensions - Interface for runtime extension install/uninstall operations
• FirefoxOptions - Accepts a profile containing extensions
• FirefoxDriver - Launches Firefox with the configured profile and extensions