1Profiles
2========
3
4geckodriver uses [profiles] to instrument Firefox’ behaviour.  The
5user will usually rely on geckodriver to generate a temporary,
6throwaway profile.  These profiles are deleted when the WebDriver
7session expires.
8
9In cases where the user needs to use custom, prepared profiles,
10geckodriver will make modifications to the profile that ensures
11correct behaviour.  See [_Automation preferences_] below on the
12precedence of user-defined preferences in this case.
13
14Custom profiles can be provided two different ways:
15
16  1. by appending `--profile /some/location` to the [`args` capability],
17     which will instruct geckodriver to use the profile _in-place_;
18
19  2. or by setting the [`profile` capability] to a Base64-encoded
20     ZIP of the profile directory.
21
22Note that geckodriver has a [known bug concerning `--profile`] that
23prevents the randomised Marionette port from being passed to
24geckodriver.  To circumvent this issue, make sure you specify the
25port manually using `--marionette-port <port>`.
26
27The second way is compatible with shipping Firefox profiles across
28a network, when for example the geckodriver instance is running on
29a remote system.  This is the case when using Selenium’s `RemoteWebDriver`
30concept, where the WebDriver client and the server are running on
31two distinct systems.
32
33[profiles]: https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
34[_Automation preferences_]: #automation-preferences
35[`args` capability]: ./Capabilities.html#capability-args
36[`profile` capability]: ./Capabilities.html#capability-profile
37[known bug concerning `--profile`]: https://github.com/mozilla/geckodriver/issues/1058
38
39
40Default locations for temporary profiles
41----------------------------------------
42
43When a custom user profile is not provided with the `-profile`
44command-line argument geckodriver generates a temporary, throwaway
45profile.  This is written to the default system temporary folder
46and subsequently removed when the WebDriver session expires.
47
48The default location for temporary profiles depends on the system.
49On Unix systems it uses /tmp, and on Windows it uses the Windows
50directory.
51
52The default location can be overridden.  On Unix you set the `TMPDIR`
53environment variable.  On Windows, the following environment variables
54are respected, in order:
55
56  1. `TMP`
57  2. `TEMP`
58  3. `USERPROFILE`
59
60It is not necessary to change the temporary directory system-wide.
61All you have to do is make sure it gets set for the environment of
62the geckodriver process:
63
64	% TMPDIR=/some/location ./geckodriver
65
66
67Automation preferences
68----------------------
69
70As indicated in the introduction, geckodriver configures Firefox
71so it is well-behaved in automation environments.  It uses a
72combination of preferences written to the profile prior to launching
73Firefox (1), and a set of recommended preferences set on startup (2).
74
75These can be perused here:
76
77  1. [testing/geckodriver/src/prefs.rs](https://searchfox.org/mozilla-central/source/testing/geckodriver/src/prefs.rs)
78  2. [testing/marionette/components/marionette/marionette.js](https://searchfox.org/mozilla-central/source/testing/marionette/components/marionette.js)
79
80As mentioned, these are _recommended_ preferences, and any user-defined
81preferences in the [user.js file] or as part of the [`prefs` capability]
82take precedence.  This means for example that the user can tweak
83`browser.startup.page` to override the recommended preference for
84starting the browser with a blank page.
85
86The recommended preferences set at runtime (see 2 above) may also
87be disabled entirely by setting `marionette.prefs.recommended`.
88This may however cause geckodriver to not behave correctly according
89to the WebDriver standard, so it should be used with caution.
90
91Users should take note that the `marionette.port` preference is
92special, and will always be overridden when using geckodriver unless
93the `--marionette-port <port>` flag is used specifically to instruct
94the Marionette server in Firefox which port to use.
95
96[user.js file]: http://kb.mozillazine.org/User.js_file
97[`prefs` capability]: ./Capabilities.html#capability-prefs
98
99
100Temporary profiles not being removed
101------------------------------------
102
103It is a known bug that geckodriver in some instances fails to remove
104the temporary profile, particularly when the session is not explicitly
105deleted or the process gets interrupted.  See [geckodriver issue
106299] for more information.
107
108[geckodriver issue 299]: https://github.com/mozilla/geckodriver/issues/299
109