feincms3-cookiecontrol

Despite its name and the fact that it is documented as a part of feincms3, feincms3-cookiecontrol can also be used standalone.

Some jurisidictions require the the users' consent before adding analytics scripts and tracking cookies. While it may be best to not use any analytics and tracking at all this may not be possible or even desirable in all circumstances.

Many solutions exist for adding a consent banner to the website. Some of those banners require loading JavaScript and other assets from external servers. This raises some questions because loading those scripts may also be seen as tracking already. It is certainly safer to implement a cookie control panel locally. It would be boring to start from scratch on each site.

This guide explains how to use feincms3-cookiecontrol.

Install the package:

pip install feincms3-cookiecontrol

Add feincms3_cookiecontrol to INSTALLED_APPS:

INSTALLED_APPS = [
    # ...
    "feincms3_cookiecontrol",
]

Apply the initial migration:

python manage.py migrate

Add the panel to the template, e.g. in base.html at the end of the <body> element:

<!doctype html>
<html>
  ...
  <body>
    ...
    {% load feincms3_cookiecontrol %}{% feincms3_cookiecontrol %}
  </body>
</html>

You'll have to add all tracking scripts yourself now.

The presentation of the panel is a fixed banner at the bottom of the viewport. Once any cookies have been accepted (essential cookies have to be accepted, e.g. the CSRF cookie) the banner is replaced by a single button which allows showing the control panel again.

The default colors of the control panel may not fit into your site. The best way to customize the appearance is to set a few CSS variables, e.g.:

.f3cc {
  --f3cc-background: #e9e9e9;
  --f3cc-foreground: #000000;
  --f3cc-button-background: #cbcbcb;
  --f3cc-accept-background: #90f690;
  --f3cc-button-foreground: #cbcbcb;
  --f3cc-accept-foreground: #cbcbcb;
}

It's recommended to set all variables if you set a single one; the exception is --f3cc-button-foreground which defaults to the value of --f3cc-foreground and --f3cc-accept-foreground which defaults to the value of --f3cc-button-foreground.

You may want to suppress the button to modify the consent on some pages, for example on all pages except for the privacy policy. A good way to achieve this follows.

Let's assume you're using page types as described in the feincms3 templates and regions guide. Let's also assume that your privacy policy page uses the standard page type described in the guide:

class Page(AbstractPage, PageTypeMixin):
    TYPES = [
        TemplateType(
            key="standard",
            title=_("standard"),
            template_name="pages/standard.html",
            regions=[
                Region(key="main", title=_("Main")),
            ],
        ),
    ]

We will add an additional page type which can be used as a marker. Since we're using feincms3 apps be sure to read the introduction to feincms3 apps if you haven't done this already. You may also want to take a look at the feincms3 root passthru reference.

class Page(AbstractPage, PageTypeMixin):
    TYPES = [
        TemplateType(
            key="standard",
            title=_("standard"),
            template_name="pages/standard.html",
            regions=[
                Region(key="main", title=_("Main")),
            ],
        ),
        ApplicationType(
            key="privacy-policy",
            title=_("privacy policy"),
            urlconf="feincms3.root.passthru",
            template_name="pages/standard.html",
            regions=[
                Region(key="main", title=_("Main")),
            ],
        ),
    ]

Now you can extend the page_context helper:

from feincms3.root.passthru import reverse_passthru

def page_context(request, *, page=None):
    ...
    context = {
        ...
    }
    if url := reverse_passthru("privacy-policy", fallback=None):
        context["privacy_policy_url"] = request.build_absolute_uri(url)
    return context

Now you can use this additional variable in the template:

<!doctype html>
<html>
  ...
  <body>
    ...
    {% load feincms3_cookiecontrol %}
    {% feincms3_cookiecontrol privacy_policy_url=privacy_policy_url %}
  </body>
</html>

The frontend code will automatically add a link to the privacy policy to the banner's content and will only show the modify button if the current location matches the privacy policy's URL.

The panel can be integrated into another site by following these steps.

Set the domain for the cookie so that the cookie is available on subdomains (be sure to check the relevant guides to understand what the problems may be when doing this and what restrictions you have to honor):

COOKIECONTROL = {"domain": "example.com"}

Add the view and optionally provide the privacy policy URL:

from feincms3.root.passthru import reverse_passthru_lazy
from feincms3_cookiecontrol.views import inject

urlpatterns = [
    # Base case
    path("f3cc-inject.js", inject),

    # Using reverse_passthru_lazy.
    # NOTE! The inject view uses `request.build_absolute_uri` to
    # complete the URL, you do not have to add the domain and
    # protocol yourself here.
    path(
        "f3cc-inject.js",
        inject,
        {"privacy_policy_url": reverse_passthru_lazy("privacy-policy", fallback="/")},
    ),
]

Embed the script:

<script async src="https://example.com/f3cc-inject.js"></script>

Google Tag Manager and the Google tags it loads expect to be told about the visitor's consent through Consent Mode. Google describes two ways of implementing it, basic and advanced. Use one or the other, never both.

Basic: Google's scripts are only loaded after the visitor has accepted all cookies, which is what the package does anyway. GTM doesn't go into your templates at all; base.html only contains the banner as usual:

{% load feincms3_cookiecontrol %}
<!doctype html>
<html>
  <head>
    ...
  </head>
  <body>
    ...
    {% feincms3_cookiecontrol %}
  </body>
</html>

Add a cookie control script in the Django admin instead, containing the consent defaults followed by the GTM snippet. All four consent signals are granted, which is the truth by the time the script is injected:

<script>
  window.dataLayer = window.dataLayer || []
  function gtag() { dataLayer.push(arguments) }
  gtag("consent", "default", {
    ad_user_data: "granted",
    ad_personalization: "granted",
    ad_storage: "granted",
    analytics_storage: "granted",
  })
</script>
<!-- Google Tag Manager -->
<script>(function(w,d,s,l,i){...})(window,document,'script','dataLayer','GTM-XXXXXXX');</script>

Advanced: GTM is loaded on every page, with all signals defaulting to denied. Until the visitor accepts, Google sets no cookies and sends cookieless pings instead, which Google uses to model the conversions it doesn't observe. Load f3cc/consent-mode-advanced.js synchronously in the <head>, before the GTM snippet, and add the GTM snippet to the template itself instead of to a cookie control script (and don't add the basic mode's script either):

{% load feincms3_cookiecontrol static %}
<!doctype html>
<html>
  <head>
    ...
    {# Keep this script synchronous: no async, defer or type="module". #}
    <script src="{% static 'f3cc/consent-mode-advanced.js' %}"></script>
    <!-- Google Tag Manager -->
    <script>(function(w,d,s,l,i){...})(window,document,'script','dataLayer','GTM-XXXXXXX');</script>
  </head>
  <body>
    ...
    {% feincms3_cookiecontrol %}
  </body>
</html>

The banner tag stays where it always is, at the end of the <body> element; it dispatches the events which consent-mode-advanced.js turns into consent updates.

The order matters: Google's tags read the consent state from the data layer when they initialize, and if no consent default is there yet they report the consent state as missing instead of denied. Do not add async, defer or type="module" to the script tag, and do not move it below the GTM snippet; any of these lets GTM initialize first. The script also reads the f3cc cookie right away and pushes a consent update for visitors who have accepted all cookies on an earlier visit, so GTM's wait_for_update isn't necessary.

The script sets the defaults to denied and enables ads_data_redaction. It updates the signals to granted when the visitor accepts all cookies (or has done so on an earlier visit), and back to denied when they withdraw their consent using the modify button.

The banner's default texts are written for the basic case; refusing non-essential cookies stays literally true, but the description suggests that nothing is sent to Google without consent. Adjust at least the description through the COOKIECONTROL setting, e.g.:

from django.utils.translation import gettext_lazy as _

COOKIECONTROL = {
    "description": _(
        "We use Google Tag Manager on every page. Without your consent,"
        " Google sets no cookies, but still receives technical data such as"
        " your IP address and the visited page. Read our {link_start}privacy"
        " policy{link_end} to find out more."
    ),
}

{link_start} and {link_end} are replaced with a link to the privacy policy if privacy_policy_url is passed to the template tag, and removed otherwise. heading, buttonAccept and buttonReject can be overridden the same way.

If users do not consent to your cookie policy, embedding third party scripts or iframes might violate data protection laws, since personal data is transfered to a third party without the users knowledge or consent. One way is to disable third party content alltogether or selectively asking users to consent to the data policies of specific providers. The letter is accomplished by the 'conscious embed' functionality.

You have to install the feincms3-cookiecontrol[embedding] extra for this to work.

Extend default providers in your settings.py:

EMBED_PROVIDERS = {
    "some-provider": {
        "title": "Mailchimp",
        "privacy_policy_url": "https://mailchimp.com/legal/privacy/",
    },
}

Surround the embedded code with the template block embed:

...
{% load feincms3_cookiecontrol %}
...
<div class="container">
    {% wrap "mailchimp" %}
    <script src="https://some-provider.com/example.js"></script>
    {% endwrap %}
</div>
...

Users that did not consent to your general cookie policy will now get asked to allow embedding content of specific providers.

You can also wrap your default renderer for embedded content plugins like feincms3.plugins.external or feincms3.embedding, but you have to explicitly specify the provider (as above with the {% wrap %} template tag).

If HTML is added dynamically to the site which contains such embedded fragments you have to call the f3ccRenderEmbeds() JavaScript function yourself to embed the third party content which has already been accepted by the user.

The feincms3_cookiecontrol.embedding module also offers an embed function where you can only pass an URL and either you get back the wrapped embed code or nothing at all. You may also specify your own embed providers; in this case you should also add a handler key to the EMBED_PROVIDERS setting; the function only receives the URL and returns either the embedding HTML or None if the URL isn't using the provider at all. At the time of writing the module supports embedding YouTube and Vimeo URLs.

You may use the embed shortcut as follows:

# ...
from feincms3_cookiecontrol.embedding import embed
# ...
class EmbeddedVideo(plugins.external.External, PagePlugin):
    # ...
    def embedded_html(self):
        return embed(self.url)

The same functionality is also available directly in templates:

...
{% load feincms3_cookiecontrol %}
{% embed plugin.url %}
...

For URLs not handled by any of the providers above you can fall back to feincms3_cookiecontrol.embedding.oembed. It fetches the embed code using oEmbed and wraps it in a <div class="responsive-embed widescreen {provider}"> element inside the usual consent prompt. The provider is the slugified provider_name of the oEmbed response, so consent is given per oEmbed provider.

By default oembed uses feincms3.plugins.external.oembed_json which asks Noembed for the embed code. Asking a third party service may not be what you want; pass your own oembed_json callable instead. It receives the URL and has to return the oEmbed response as a dictionary, or a falsy value if the URL cannot be embedded. Using micawber which talks to the providers directly:

# app/oembed.py
from django.core.cache import cache
from micawber import ProviderException, bootstrap_basic, bootstrap_oembed

providers = bootstrap_oembed(cache, registry=bootstrap_basic(), timeout=5)


def oembed_json(url):
    try:
        return providers.request(url)
    except ProviderException:
        return None

Try the built-in providers first and only fall back to oEmbed afterwards, e.g. in a renderer for a plugin with an url field:

from feincms3_cookiecontrol.embedding import embed, oembed

from app.oembed import oembed_json


def render_external(plugin, context):
    return embed(plugin.url) or oembed(plugin.url, oembed_json=oembed_json)

Both functions return an empty string if they cannot embed the URL. Note that the embed code is used as-is, so only use oembed with URLs entered by trusted users. You probably want some CSS to size the embeds, for example:

.responsive-embed,
.f3cc-embed {
  aspect-ratio: 16 / 9;
}

.responsive-embed {
  position: relative;
}

.responsive-embed iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}