Add Halloween effects to Ghost

Ghost has site-wide code injection built in, so no theme edit is needed.

Steps

Open Settings → Advanced → Code injection in Ghost Admin. Some versions list Code injection directly under Settings.
Paste the snippet below into Site footer.
Save and reload your site.

The snippet

One paste, no other files. It loads halloween.js 1.0.3 from jsDelivr and turns on webs in two corners, blinking eyes, flying witches, a dropping spider and a rising tombstone.

<script src="https://cdn.jsdelivr.net/npm/halloween.js@1.0.3/dist/halloween.iife.js"></script>
<script>
(function () {
  function apply() {
    document.body.classList.add("halloween", "halloween-screen-left-top", "halloween-screen-right-bottom", "halloween-eyes", "halloween-witches", "halloween-spider-drop", "halloween-tombstones");
  }
  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", apply);
  } else {
    apply();
  }
})();
</script>

Make it yours

Pick corners, effects, intensity, color and season dates in the playground and open the Paste-only tab. It produces this same snippet, library line included, with your choices.

Good to know

The effects only appear in a window around Halloween, 18 October to 2 November by default. Change the dates in the playground to see them on another day.
Ambient effects stop when a visitor has reduced motion turned on. The screen-corner webs stay.
The effects sit in a fixed layer and never shift your page layout.
Ghost outputs the Site footer field just before the closing </body> tag on every page.
Nothing showing? Reload without cache, then check that the snippet is on the live site and that no content blocker is stripping it.

Other platforms

All options on the halloween.js home page, full documentation on GitHub.