SeleniumHQ/selenium · error · OSError

Add-on path does not exist: {addon_path}

Error message

Add-on path does not exist: {addon_path}

What it means

Raised by FirefoxProfile's add-on manifest parser when the addon_path passed to it does not exist on the filesystem (os.path.exists returns False). The library validates the path before attempting any zip or directory read, so the user gets a clear error instead of a cryptic downstream failure.

Source

Thrown at py/selenium/webdriver/firefox/firefox_profile.py:275

                    rc.append(node.data)
            return "".join(rc).strip()

        def parse_manifest_json(content):
            """Extract details from the contents of a WebExtensions manifest.json file."""
            manifest = json.loads(content)
            try:
                id = manifest["applications"]["gecko"]["id"]
            except KeyError:
                id = manifest["name"].replace(" ", "") + "@" + manifest["version"]
            return {
                "id": id,
                "version": manifest["version"],
                "name": manifest["version"],
                "unpack": False,
            }

        if not os.path.exists(addon_path):
            raise OSError(f"Add-on path does not exist: {addon_path}")

        try:
            if zipfile.is_zipfile(addon_path):
                with zipfile.ZipFile(addon_path, "r") as compressed_file:
                    if "manifest.json" in compressed_file.namelist():
                        return parse_manifest_json(compressed_file.read("manifest.json"))

                    manifest = compressed_file.read("install.rdf")
            elif os.path.isdir(addon_path):
                manifest_json_filename = os.path.join(addon_path, "manifest.json")
                if os.path.exists(manifest_json_filename):
                    with open(manifest_json_filename, encoding="utf-8") as f:
                        return parse_manifest_json(f.read())

                with open(os.path.join(addon_path, "install.rdf"), encoding="utf-8") as f:
                    manifest = f.read()
            else:
                raise OSError(f"Add-on path is neither an XPI nor a directory: {addon_path}")

View on GitHub (pinned to aa36b38e69)

Solutions

1. Verify the path exists with os.path.exists(addon_path) before calling the API
2. Use an absolute path constructed with os.path.abspath or pathlib.Path.resolve()
3. Ensure the .xpi or addon directory is present in CI by checking it into the repo or downloading it as a build step

Example fix

// before
profile.add_extension('addons/myplugin')

// after
import os
addon = os.path.abspath('addons/myplugin')
assert os.path.exists(addon), f'Addon not found at {addon}'
profile.add_extension(addon)

import os
addon_path = 'addons/myplugin.xpi'
if not os.path.exists(addon_path):
    raise FileNotFoundError(f'Addon path does not exist: {addon_path}')
profile.add_extension(addon_path)

try:
    profile.add_extension(addon_path)
except OSError as e:
    print(f'Addon path invalid: {e}')
    addon_path = resolve_addon_path()  # fallback logic

When it happens

Trigger: Calling the add-on install/parse API with a path to an .xpi file or directory that does not exist, a relative path resolved from the wrong working directory, or a typo in the path string.

Common situations: Relative paths that break when tests run from a different CWD. CI environments where addon files are not copied into the working tree. Paths with typos or wrong file extensions.

Related errors

• Add-on path is neither an XPI nor a directory: {addon_path}
• {str(e)}
• Add-on id could not be found.
• could not find extension at #{path.inspect}
• Couldn't find manifest.json in ${extension}

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/a505e1e49e240290. Report an issue: GitHub.