mozrunner

library8.4.0pypypi✓ verified 84d ago

A library to reliably start, stop, and configure Mozilla applications (Firefox, Thunderbird, etc.). Version 8.4.0 supports Python >=3.8. It wraps Mozilla processes with geckodriver or Marionette for automation and testing.

testing devops

pip install mozrunner

package ↗homepage ↗

INSTALL

IMPORT

SIG · MOZRUNNER

mozrunner

testingpythonv8.4.0

Install

3.7s avg

Import

474ms

Disk

26MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v8.4.0 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.500s · 30.8MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 3.7s · import 0.448s · 31MB

26MB installed

● package 26MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Runner

✓ from mozrunner import Runner

✗ mozrunner.Runner

Most classes are top-level in the mozrunner package, not nested.

FirefoxRunner

✓ from mozrunner import FirefoxRunner

✗ from mozrunner.runners import FirefoxRunner

FirefoxRunner is exported directly from mozrunner; no submodule needed.

Create a Firefox profile, start the browser, wait, then stop.

from mozrunner import FirefoxRunner from mozprofile import FirefoxProfile profile = FirefoxProfile() # or use addons/prefs runner = FirefoxRunner(binary='firefox', profile=profile) runner.start() print('Firefox started') runner.wait(timeout=60) runner.stop()

Debug

Known issues

gotchaBinary path must point to a Firefox/Thunderbird executable. If not found, Runner raises an OSError or fails silently. Always verify the binary path.

fix

Specify the full path or ensure 'firefox' is on PATH. Use shutil.which('firefox').

affects: all

deprecatedThe 'mozrunner.cli' module and command-line interface (CLI) are deprecated and may be removed in the future.

fix

Use the library API directly instead of the CLI wrapper.

affects: >=8.0.0

gotchaThe 'Runner' base class does not automatically download or update GeckoDriver. You must manage GeckoDriver separately for Firefox automation.

fix

Install geckodriver and ensure it's on PATH before using mozrunner with Marionette-based automation.

affects: all

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'mozrunner'

Package not installed or installed in a different virtual environment.

fix

Run `pip install mozrunner` in the correct environment.

AttributeError: module 'mozrunner' has no attribute 'Runner'

Outdated installation (version <8.0.0) where Runner was in a submodule.

fix

Upgrade: `pip install -U mozrunner`. Also check imports: use `from mozrunner import Runner`.

OSError: [Errno 2] No such file or directory: 'firefox'

The browser binary is not on PATH or the specified path is wrong.

fix

Pass the correct binary path: binary='/usr/bin/firefox' or use shutil.which('firefox').

Upgrade

Version history

8.4.0latest on PyPI · released Mar 26, 2026

Audit

Dependencies

mozprofilerequiredUsed internally to manage Firefox profiles.

mozprocessrequiredUsed to start/kill browser processes.

mozinforequiredProvides platform information for binary paths.

sixoptionalCompatibility layer for Python 2/3 (mostly deprecated usage).

Agent activity

5 hits · last 30 days

node

Amazon

Resources

packagehttps://pypi.org/project/mozrunner/ ↗

homepagehttps://wiki.mozilla.org/Auto-tools/Projects/Mozbase ↗