diff --git a/src/api/admin/pages/deploy.rs b/src/api/admin/pages/deploy.rs
index 13cfeb9..0195b61 100644
--- a/src/api/admin/pages/deploy.rs
+++ b/src/api/admin/pages/deploy.rs
@@ -9,14 +9,52 @@ use super::shared::{html_escape, require_admin};
 use crate::api::error::ApiError;
 use crate::api::middleware::AuthedUser;
 use axum::extract::Form;
+use axum::http::HeaderMap;
 use axum::response::Html;
 use serde::Deserialize;
 use serde_json::json;
 
-pub async fn index(admin: AuthedUser) -> Result<Html<String>, ApiError> {
+pub async fn index(admin: AuthedUser, headers: HeaderMap) -> Result<Html<String>, ApiError> {
     require_admin(&admin)?;
     let pubkey = read_pubkey();
-    Ok(Html(render_form(&pubkey, "", "", "", "", None)))
+    // Best-effort prefill: the Host the admin's browser is currently
+    // talking to is almost always the same machine running hbbs, so it's
+    // the right default for the rendezvous-host field. Reverse proxies
+    // forward the original Host through unless explicitly stripped, so
+    // this works behind nginx/Caddy/Traefik too. Operator can edit if
+    // hbbr lives on a different host.
+    let host_default = headers
+        .get(axum::http::header::HOST)
+        .and_then(|v| v.to_str().ok())
+        .map(host_only)
+        .unwrap_or("")
+        .to_string();
+    let (api_default, relay_default) = if host_default.is_empty() {
+        (String::new(), String::new())
+    } else {
+        (format!("https://{}", host_default), host_default.clone())
+    };
+    Ok(Html(render_form(
+        &pubkey,
+        &host_default,
+        &api_default,
+        &relay_default,
+        "",
+        None,
+    )))
+}
+
+/// Strip an optional `:port` (and IPv6 brackets) from a Host-header value.
+/// "rustdesk.example.com:21114"  -> "rustdesk.example.com"
+/// "[::1]:21114"                 -> "::1"
+/// "10.196.83.110"               -> "10.196.83.110"
+fn host_only(s: &str) -> &str {
+    if let Some(rest) = s.strip_prefix('[') {
+        if let Some(end) = rest.find(']') {
+            return &rest[..end];
+        }
+    }
+    s.rsplit_once(':').map(|(h, _)| h).unwrap_or(s)
 }
 
 #[derive(Debug, Deserialize)]
@@ -117,7 +155,14 @@ fn render_form(
       <label class="block text-xs font-medium text-slate-400 mb-1" for="host">Rendezvous host (required)</label>
       <input id="host" name="host" type="text" required value="{host}"
         placeholder="rustdesk.example.com or 203.0.113.10"
-        oninput="document.getElementById('api').placeholder='http://'+this.value+':21114'"
+        oninput="
+          const h = this.value.trim();
+          const api = document.getElementById('api');
+          const relay = document.getElementById('relay');
+          if (api.dataset.derived !== '0') api.value = h ? 'https://' + h : '';
+          if (relay.dataset.derived !== '0') relay.value = h;
+          api.placeholder = h ? 'https://' + h : 'https://rustdesk.example.com';
+        "
         class="w-full bg-slate-800 border border-slate-700 rounded px-3 py-2 text-sm focus:outline-none focus:border-sky-500" />
       <p class="text-xs text-slate-500 mt-1">The hostname or IP clients reach hbbs at (TCP/UDP 21116).</p>
     </div>
@@ -125,15 +170,17 @@ fn render_form(
     <div>
       <label class="block text-xs font-medium text-slate-400 mb-1" for="api">API URL (optional)</label>
       <input id="api" name="api" type="text" value="{api}"
-        placeholder="http://host:21114"
+        placeholder="https://rustdesk.example.com"
+        oninput="this.dataset.derived = '0';"
         class="w-full bg-slate-800 border border-slate-700 rounded px-3 py-2 text-sm focus:outline-none focus:border-sky-500" />
-      <p class="text-xs text-slate-500 mt-1">Full URL of this admin/login API. Leave blank to disable login on the client.</p>
+      <p class="text-xs text-slate-500 mt-1">Full URL of this admin/login API. Defaults to <code>https://&lt;host&gt;</code>; edit if your API runs on a different scheme/port. Leave blank to disable login on the client.</p>
     </div>
 
     <div>
       <label class="block text-xs font-medium text-slate-400 mb-1" for="relay">Relay host (optional)</label>
       <input id="relay" name="relay" type="text" value="{relay}"
         placeholder="rustdesk.example.com"
+        oninput="this.dataset.derived = '0';"
         class="w-full bg-slate-800 border border-slate-700 rounded px-3 py-2 text-sm focus:outline-none focus:border-sky-500" />
       <p class="text-xs text-slate-500 mt-1">Only set if hbbr runs on a separate host; otherwise leave blank.</p>
     </div>