SeleniumHQ/selenium · error · OSError

Can't find java on system PATH. JRE is required to run the…

Error message

Can't find java on system PATH. JRE is required to run the Selenium server

What it means

Raised in `start()` when `self.java_path` is unset AND `shutil.which('java')` returns None, i.e. no `java` binary is discoverable on the system PATH. Running the Selenium server JAR requires a JRE, so without java the process cannot be built. It is an OSError.

Solutions

1. Install a JRE/JDK (e.g. apt-get install -y default-jre, or a temurin image).
2. Ensure java's bin directory is on PATH: `which java` must succeed in the same shell.
3. Alternatively set server.java_path to an absolute java binary you have verified exists.

Example fix

# before
# (no java installed)
server.start()

# after (Dockerfile)
# RUN apt-get update && apt-get install -y default-jre-headless
server.start()

import shutil
if server.java_path is None and shutil.which('java') is None:
    raise EnvironmentError('java/JRE not installed or not on PATH; install a JRE before start()')

When it happens

Trigger: Calling `server.start()` on a host/container that has no JDK/JRE installed, or where java is installed but its bin directory is not on PATH. Also when PATH is overridden/reset in the spawned environment (env setter) to exclude java's location.

Common situations: Minimal Docker images (python:slim) with no JVM. CI runners where java is installed under a toolchain manager (sdkman/asdf) that hasn't been activated for the shell. SSH sessions with a trimmed PATH.

Related errors

• Can't find java executable located at
• env must be a mapping of environment variables
• log_level must be one of
• Selenium server isn't running
• Timed out waiting for Selenium server at

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/f6950e4c08968c95. Report an issue: GitHub.

Appendix: source

Thrown at py/selenium/webdriver/remote/server.py:189

        Latest version is downloaded unless specified.
        """
        args = ["--grid"]
        if version is not None:
            args.append(version)
        return SeleniumManager().binary_paths(args)["driver_path"]

    def start(self):
        """Start the server.

        Selenium Manager will detect the server location and download it if necessary,
        unless an existing server path was specified.
        """
        path = self.download_if_needed(self.version) if self.path is None else self.path

        java_path = self.java_path or shutil.which("java")
        if java_path is None:
            raise OSError("Can't find java on system PATH. JRE is required to run the Selenium server")

        command = [
            java_path,
            "-jar",
            path,
            "standalone",
            "--port",
            str(self.port),
            "--log-level",
            self.log_level,
            *self.args,
        ]
        if self.host is not None:
            command.extend(["--host", self.host])

        host = self.host if self.host is not None else "localhost"

        try:

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