Configuration

The add-on has one setting, not_assigned. Publish the config file to change it:

php artisan vendor:publish --tag=statamic-multisite-forms-config

That writes config/statamic-multisite-forms.php.

Key	Values	Default
not_assigned	empty, 404	empty

not_assigned

What the {{ form }} tags (form:create, the {{ form:contact }} shorthand, form:errors, form:success, form:submission and form:submissions) do with a form that is not assigned to the site the page is rendered for:

Value	Effect
empty (default)	Renders nothing, and form:submissions renders as it does for a form with no submissions, so a no_results branch still shows. A warning naming the form and the site is logged at warning level, once per form and site per request, so a shared layout that renders the form on every page logs one line per page view rather than one per tag.
404	Aborts the request with the site's 404 page, as Statamic's {{ 404 }} tag does. If the 404 page's layout renders the same form, it renders nothing there rather than aborting again.

The setting is checked each time the add-on boots, for every request and artisan command: any other value, including null from an unset env() variable, is logged at error level naming the setting and the value. A page that meets an unassigned form with such a value then fails with the same message, since the add-on cannot tell which behavior was meant. Pages with no unassigned form are unaffected.

form:fields inside form:create needs no gate of its own: it renders only the fields form:create hands it.

A form assigned to the page's site, and a form with no sites, render as Statamic renders them. A submit to a form from a site it is not assigned to always answers 404, whatever not_assigned says.

A submit's site is the site whose URL the request's referrer falls under, or the default site when there is none, the same rule Statamic uses to choose a submission's email locale. That site decides the 404, the site recorded on the submission, and the site's overrides. The referrer is sent by the browser, so this decides which forms a site offers and accepts; it does not stop someone who crafts a request from submitting as any site the form is assigned to.

Fetching form:create without a template

Fetched with no template to render, as Statamic::tag('form:create')->params(['in' => 'contact'])->fetch() does in Blade or PHP, form:create returns the form's data as an array, as Statamic's does. Under empty, an unassigned form returns an empty array instead, so guard the markup that reads it:

@php($form = Statamic::tag('form:create')->params(['in' => 'contact'])->fetch())
@if ($form)
    <form method="{{ $form['attrs']['method'] }}" action="{{ $form['attrs']['action'] }}">
        ...
    </form>
@endif

Without the guard, reading $form['attrs'] fails on a site the form is not assigned to.

To hide what surrounds a form on such a site, such as a heading, use the form:assigned tag.