diff --git a/js/contact.js b/js/contact.js
new file mode 100644
index 0000000..a94a157
--- /dev/null
+++ b/js/contact.js
@@ -0,0 +1,72 @@
+import { buildMailtoUrl } from "./mailto.js";
+
+/** The address the contact form messages are sent to. */
+export const MAILTO_TARGET = "hello@example.com";
+
+/**
+ * Collect form field values by name.
+ * Works with a real DOM form and with the minimal fake form used in tests.
+ *
+ * @param {{querySelectorAll(selector: string): ArrayLike<{name: string, value: string}>}} form
+ * @returns {{name: string, email: string, message: string}}
+ */
+export function readFormValues(form) {
+  const values = {};
+  for (const el of form.querySelectorAll("[name]")) {
+    values[el.name] = el.value;
+  }
+  return values;
+}
+
+/**
+ * Build the mailto: URL for the contact form from the entered values.
+ *
+ * @param {{name: string, email: string, message: string}} values
+ * @param {string} [to]
+ * @returns {string}
+ */
+export function buildContactMailto(values, to = MAILTO_TARGET) {
+  const subject = `Contact form submission from ${values.name || "someone"}`;
+  const body = [
+    `Name: ${values.name || ""}`,
+    `Email: ${values.email || ""}`,
+    "",
+    "Message:",
+    values.message || "",
+  ].join("\n");
+  return buildMailtoUrl({ to, subject, body });
+}
+
+/**
+ * Handle a contact form submit: build the mailto: URL and send the
+ * visitor to it so their mail client opens pre-filled.
+ *
+ * @param {HTMLFormElement} form
+ * @param {{to?: string, navigate?: (url: string) => void}} [options]
+ * @returns {string} the mailto: URL that was navigated to
+ */
+export function handleContactSubmit(
+  form,
+  { to = MAILTO_TARGET, navigate = (url) => { window.location.href = url; } } = {}
+) {
+  const url = buildContactMailto(readFormValues(form), to);
+  navigate(url);
+  return url;
+}
+
+/**
+ * Wire the submit handler onto a contact form.
+ * @param {HTMLFormElement} form
+ */
+export function initContactForm(form) {
+  form.addEventListener("submit", (event) => {
+    event.preventDefault();
+    handleContactSubmit(form);
+  });
+}
+
+// Browser-only wiring — guarded so this module stays importable in Node tests.
+if (typeof window !== "undefined" && typeof document !== "undefined") {
+  const form = document.getElementById("contact-form");
+  if (form) initContactForm(form);
+}