SlimerJS runs on any platform on which Firefox is available: Linux (32bits and 64bits), Windows, MacOs X.

On windows, you should open a terminal. You can use the classical cmd.exe, or the recent PowerShell.exe. You can also install Cygwin and use its terminal.

You cannot use the MingW32 environment on Windows because there are some issues with ir (no output in the console, and it lacks on some commands like mktemp).

Note: version 0.9 and lower of SlimerjS were provided with XulRunner, the Firefox runtime. After release of XulRunner 40.0, Mozilla ceased to build it and even remove its source code from Firefox’s source tree. So you have to install Firefox to use SlimerJS 0.10 and higher.

On Linux, if you don’t have an X environment, and if you want to install Firefox from binaries provided directly by Mozilla, you need to know that Firefox needs these libraries:,,,,,,,,,, This list may not be complete, depending of your distribution

and the version of Firefox. On Ubuntu/Debian, you can install/verify it by doing:
sudo apt-get install libc6 libstdc++6 libgcc1 libgtk2.0-0 libasound2 libxrender1 libdbus-glib-1-2

If Firefox or SlimerJS does not work, add --debug=true to the command line of Slimerjs, to see if there is no errors about libraries missing. If so, install packages that provide missing libraries. Search missing files in the debian repository or the the ubuntu repository.

Probably the best thing is to install the package of Firefox provided by your distribution : it will install all dependencies. And next, you can install and use binaries from Mozilla.

Installation of SlimerJS

To install SlimerJS, you need to download its package. This is a zip package containing SlimerJS and it targets all operating system. You have to install Firefox separately (version 40+ is recommanded) and probably you’ll need to set an environment variable. This package can be downloaded from Or it can be installed from a repository like the Arch Linux’s repository or Homebrew.

See the download page to know the places from where you can retrieve SlimerJS.

Configuring SlimerJS

During its launch, SlimerJS tries to discover itself the path of Firefox.

In case it fails, or if you want to launch SlimerJS with a specific version of Firefox, you should create an environment variable containing the path of the Firefox binary. To create this environment variable from a command line:

  • On linux:
    export SLIMERJSLAUNCHER=/usr/bin/firefox
  • on Windows
    SET SLIMERJSLAUNCHER="c:\Program Files\Mozilla Firefox\firefox.exe
  • On windows with cygwin
    export SLIMERJSLAUNCHER="/cygdrive/c/program files/mozilla firefox/firefox.exe"
  • On MacOS
    export SLIMERJSLAUNCHER=/Applications/

You can of course set this variable in your .bashrc, .profile or in the computer properties on Windows.

Using unstable version or very old versions of Firefox

By default, SlimerJS is configured to be compatible only with specific stable versions of Firefox. It’s because internal API of Firefox can be changed between versions, and so SlimerJS may not work as expected. Stranges behaviors or even fatal errors may appears with unsupported versions. SlimerJS has only been tested with specific versions of Firefox.

However, you can change this limitation, by modifying the maxVersion parameter (and/or the minVersion) in the application.ini of SlimerJS. But remember you do it at your own risk.

If you found issues with unsupported versions of Firefox, please discuss about it in the mailing-list, especially if it is about an unstable version of Firefox.

Launching SlimerJS

From a command line, call the slimerjs executable (or slimerjs.bat for Windows) with the path of a javascript file.

/somewhere/slimerjs-1.2.3/slimerjs myscript.js
# or if SlimerJS is in your $PATH:
slimerjs myscript.js

On Windows:

c:\somewhere\slimerjs-1.2.3\slimerjs.bat myscript.js

The js script should contain your instructions to manipulate a web page...

You can indicate several options on the command line. See the “configuration” chapter.

Having a headless SlimerJS

Starting with Firefox 56, (and 55 on linux), you can add the command line option --headless, so you don’t need a graphical environment, even on Linux. See the Mozilla documentation about it.

./slimerjs --headless myscript.js

Instead of using this --headless flag, you can set an environment variable MOZ_HEADLESS to 1.

./slimerjs myscript.js

If you are using Firefox 54 and lower, the only solution to have an “headless” SlimerJS, is to use xvfb and it works only on Linux. Xvfb allows to launch any “graphical” programs without the need of an X-Windows environment. Windows of the application won’t be shown and will be drawn only in memory.

Install it from your prefered repository (sudo apt-get install xvfb with debian/ubuntu).

Then launch SlimerJS like this:

xvfb-run ./slimerjs myscript.js

You won’t see any windows. If you have any problems with xvfb, see its documentation.

Note: xvfb is also available on MacOS, however Firefox for MacOs does not using X11 backend so it does not work.

Using flash plugin or other plugins

The possibility to use Flash and other NPAPI plugins depends to the version of Firefox you are using.

Firefox 52+ is not be able any more to load NPAPI plugins. And future version may not be able to load Flash.

So SlimerJS can load Flash content or other NPAPI plugins if Firefox can. In this case, just install them as indicated by the vendor, and it will be theorically recognized by SlimerJS. See details on MDN .

For example, on linux, install the corresponding package.

Note: plugins are not Firefox/XUL/JS extensions. Plugins and “extensions” are two different things in the gecko world. Extensions for Firefox are pieces of code to extends some features of Gecko and/or to add some UI things in the interface of Firefox. Plugins are black boxes that can only be loaded with the html element <object>, like Flash, to show non-html content inside a web page.

See detailed definition of plugins on MDN .

Creating extensions?

Theorically, you can create XUL/JS addons for SlimerJS like you do for Firefox, It is not easy but it is possible. See the dedicated chapter. It is not possible any more if you are using Firefox 57+.