Install the widget with one script tag

Pick your website in the sidebar, then Website widget. The code on that screen has your project ID filled in.

Paste it before the closing body tag, or into a tag manager such as Zaraz (Custom HTML, all pageviews). The Feedback button is always visible, so use this on sites only your team and clients see.

<script
  src="https://app.margin-comments.com/widget.js"
  data-project="YOUR_PROJECT_ID"
  data-environment="staging"
  data-build="your-build-id"
  defer
></script>

Visitors get nothing: no request and no button. The loader only fetches the widget in a browser that is in review mode.

<script>
(function (d) {
  var q = location.search + location.hash;
  if (!/(^|; )margin_review=1/.test(d.cookie) &&
      !/[?&#](margin|margin_comment|margin_pair)=/.test(q)) return;
  var s = d.createElement("script");
  s.src = "https://app.margin-comments.com/widget.js";
  s.async = true;
  s.dataset.project = "YOUR_PROJECT_ID";
  s.dataset.environment = "production";
  s.dataset.mode = "review";
  d.head.appendChild(s);
})(document);
</script>

Open the website from the dashboard once with Open website. The page opens already connected, and the browser stays in review mode for 30 days. Exit review mode in the widget ends it.

Reload the page. The Margin button appears. If it does not, the widget guide for missing buttons lists the usual causes.