diff --git a/static/add_an_instance.mts b/static/add_an_instance.mts
new file mode 100644
index 0000000..e305637
--- /dev/null
+++ b/static/add_an_instance.mts
@@ -0,0 +1,54 @@
+// This file handles the "Add an instance" dialog
+
+export function parseHost(host: string): { host: string, secure: boolean } | null {
+    let parsedInstance = URL.parse(host);
+    parsedInstance ??= URL.parse("https://" + host);
+    if (!parsedInstance?.host) return null;
+    return {
+        host: parsedInstance.host,
+        secure: parsedInstance.protocol === "https:"
+    };
+}
+
+export function initializeAddInstanceDialog(dialog: HTMLDialogElement): {
+    showAddInstanceDialog: () => void,
+    hideAddInstanceDialog: () => void,
+} {
+    const showAddInstanceDialog = () => dialog.showModal();
+    const hideAddInstanceDialog = () => dialog.close();
+
+    const form = dialog.querySelector(".addInstanceForm");
+    if (!(form instanceof HTMLFormElement))
+        throw new Error(".addInstanceForm isn't a form");
+
+    const instanceHost = form.querySelector("#instanceHost");
+    if (!(instanceHost instanceof HTMLInputElement))
+        throw new Error("#instanceHost isn't an input");
+
+    instanceHost.addEventListener("input", e => {
+        if (parseHost(instanceHost.value) === null)
+            instanceHost.setCustomValidity("Invalid instance hostname or URL");
+        else
+            instanceHost.setCustomValidity("");
+    });
+
+    form.addEventListener("submit", async e => {
+        // A sane browser doesn't allow for submitting the form if the above validation fails
+        const { host, secure } = parseHost(instanceHost.value)!;
+        console.log(
+            await fetch(`/api/instance_info/${secure}/${encodeURI(host)}`).then(r => r.json())
+        );
+        form.reset();
+    });
+
+    const closeButton = form.querySelector(".close");
+    if (!(closeButton instanceof HTMLButtonElement))
+        throw new Error(".close isn't a button");
+
+    closeButton.addEventListener("click", e => hideAddInstanceDialog());
+
+    return {
+        showAddInstanceDialog,
+        hideAddInstanceDialog
+    };
+}
diff --git a/static/crossroad.html b/static/crossroad.html
index 9940a49..8fbe927 100644
--- a/static/crossroad.html
+++ b/static/crossroad.html
@@ -9,9 +9,12 @@
 </head>
 
 <body>
-    <script type="module" src="/static/crossroad.mjs"></script>
+    <script type="module">
+        Object.assign(globalThis, await import("/static/crossroad.mjs"));
+        getMainDialog().show(); // Don't show until the page is ready
+    </script>
     <div class="flex-vcenter">
-        <dialog open>
+        <dialog id="mainDialog">
             <h1>FeDirect</h1>
             <p>By Nekomata</p>
             <form>
@@ -20,14 +23,20 @@
                     Instances and stuff go here!
                 </label>
             </form>
-            <br />
-            <button onclick="document.getElementById('addInstance').showModal()">Add an instance</button>
+            <br>
+            <button onclick="showAddInstanceDialog()">Add an instance</button>
         </dialog>
     </div>
     <dialog id="addInstance">
         <h1>Add an instance</h1>
-        <form method="dialog">
-            <button>OK</button>
+        <form method="dialog" class="addInstanceForm">
+            <label for="instanceHost">Instance hostname or URL<br>
+                (for example <code>mastodon.social</code> or <code>https://kitsunes.club/</code>)<br>
+            </label>
+            <input id="instanceHost" type="text" name="instanceHost" />
+            <br>
+            <button type="submit">OK</button>
+            <button type="reset" class="close">Cancel</button>
         </form>
     </dialog>
 </body>
diff --git a/static/crossroad.mts b/static/crossroad.mts
index f624e3f..00332d4 100644
--- a/static/crossroad.mts
+++ b/static/crossroad.mts
@@ -1,5 +1,15 @@
+import { initializeAddInstanceDialog } from "./add_an_instance.mjs";
 import knownSoftware from "./known_software.mjs";
 import storageManager from "./storage_manager.mjs";
 console.log(knownSoftware);
 
 console.log(storageManager.storage.instances);
+
+export function getMainDialog(): HTMLDialogElement {
+    return document.getElementById('mainDialog') as HTMLDialogElement;
+}
+
+const dialog = document.querySelector("#addInstance");
+if (!(dialog instanceof HTMLDialogElement))
+    throw new Error("Couldn't find addInstance dialog");
+export const { showAddInstanceDialog, hideAddInstanceDialog } = initializeAddInstanceDialog(dialog);
