You can add Javascript code by multiple ways in Decidim:

Asset pipeline

Just add it to app/assets/javascripts/application.js. For example to create a new alert just add:


More information in Rails Asset Pipeline documentation.

Head extra file

There’s an special partial file for adding inline content in every public page. You just need to create a file called app/views/layouts/decidim/_head_extra.html.erb:

<script type="text/javascript">

Custom HTML Header snippets

If you need changes on a multitenant installation, you can do so by enabling a configuration in your config/initializers/decidim.rb file. Please do notice that this has security implications:

  # Custom HTML Header snippets
  # The most common use is to integrate third-party services that require some
  # extra JavaScript or CSS. Also, you can use it to add extra meta tags to the
  # HTML. Note that this will only be rendered in public pages, not in the admin
  # section.
  # Before enabling this you should ensure that any tracking that might be done
  # is in accordance with the rules and regulations that apply to your
  # environment and usage scenarios. This feature also comes with the risk
  # that an organization's administrator injects malicious scripts to spy on or
  # take over user accounts.
  config.enable_html_header_snippets = true

Then you’ll have a new textarea field called "Header snippets" in Administration → Configuration → Appearance (URL /admin/organization/appearance/edit):

Header snippet

Notice that you can resize this textarea.