mozinfo — Get system information

Throughout Mozilla python code, checking the underlying platform is done in many different ways. The various checks needed lead to a lot of copy+pasting, leaving the reader to wonder….is this specific check necessary for (e.g.) an operating system? Because information is not consolidated, checks are not done consistently, nor is it defined what we are checking for.

mozinfo proposes to solve this problem. mozinfo is a bridge interface, making the underlying (complex) plethora of OS and architecture combinations conform to a subset of values of relevance to Mozilla software. The current implementation exposes relevant keys and values such as: os, version, bits, and processor. Additionally, the service pack in use is available on the windows platform.

API Usage

mozinfo is a python package. Downloading the software and running python develop will allow you to do import mozinfo from python. is the only file contained in this package, so if you need a single-file solution, you can just download or call this file through the web.

The top level attributes (os, version, bits, processor) are available as module globals:

if mozinfo.os == 'win': ...

In addition, mozinfo exports a dictionary,, that contain these values. mozinfo also exports:

  • choices: a dictionary of possible values for os, bits, and processor

  • main: the console_script entry point for mozinfo

  • unknown: a singleton denoting a value that cannot be determined

unknown has the string representation "UNKNOWN". unknown will evaluate as False in python:

if not mozinfo.os: ... # unknown!

Command Line Usage

mozinfo comes with a command line program, mozinfo which may be used to diagnose one’s current system.

Example output:

os: linux
version: Ubuntu 10.10
bits: 32
processor: x86

Three of these fields, os, bits, and processor, have a finite set of choices. You may display the value of these choices using mozinfo --os, mozinfo --bits, and mozinfo --processor. mozinfo --help documents command-line usage.

interface to transform introspected system information to a format palatable to Mozilla

Module variables:


32 or 64


Returns True if the operating system is BSD


Returns True if the operating system is Linux


Returns True if the operating system is Mac


Returns True if the operating system is Windows


Operating system ['win', 'mac', 'linux', …]


Processor architecture ['x86', 'x86_64', 'ppc', …]


Operating system version string. For windows, the service pack information is also included

Returns information identifying the current system.

class mozinfo.StringVersion(vstring)

A string version that can be compared with comparison operators.

mozinfo.find_and_update_from_json(*dirs, **kwargs)

Find a mozinfo.json file, load it, and update global symbol table.

This method will first check the relevant objdir directory for the necessary mozinfo.json file, if the current script is being run from a Mozilla objdir.

If the objdir directory did not supply the necessary data, this method will then look for the required mozinfo.json file from the provided tuple of directories.

If file is found, the global symbols table is updated via a helper method.

If no valid files are found, this method no-ops unless the raise_exception kwargs is provided with explicit boolean value of True.

  • dirs (tuple) – Directories in which to look for the file.

  • kwargs (dict) – optional values: raise_exception: if True, exceptions are raised. False by default.


None: default behavior if mozinfo.json cannot be found. json_path: string representation of mozinfo.json path.


IOError: if raise_exception is True and file is not found.


Update the info.


new_info – Either a dict containing the new info or a path/url to a json file containing the new info.