diff --git a/src/main/frontend/components/repo.cljs b/src/main/frontend/components/repo.cljs
index 6f3b20007d..5854e5366a 100644
--- a/src/main/frontend/components/repo.cljs
+++ b/src/main/frontend/components/repo.cljs
@@ -451,8 +451,8 @@
     (-> (p/do!
          (state/<invoke-db-worker :thread-api/set-db-sync-config
                                   {:enabled? true
-                                   :ws-url config/db-sync-ws-url
-                                   :http-base config/db-sync-http-base})
+                                   :ws-url (config/db-sync-ws-url)
+                                   :http-base (config/db-sync-http-base)})
          (p/let [rsa-key-pair (state/<invoke-db-worker :thread-api/db-sync-ensure-user-rsa-keys)]
            (set-e2ee-rsa-key-ensured? (some? rsa-key-pair))))
         (p/catch (fn [e]
diff --git a/src/main/frontend/components/settings.cljs b/src/main/frontend/components/settings.cljs
index 293da4fe64..661b3cd6ef 100644
--- a/src/main/frontend/components/settings.cljs
+++ b/src/main/frontend/components/settings.cljs
@@ -547,6 +547,76 @@
                  (config-handler/set-config! :feature/enable-flashcards? value)))
              true))
 
+(defn- push-sync-config-to-worker!
+  "Push the current sync URL config to the db worker so changes take effect
+   without restarting the app."
+  []
+  (state/<invoke-db-worker :thread-api/set-db-sync-config
+                           {:enabled? true
+                            :ws-url (config/db-sync-ws-url)
+                            :http-base (config/db-sync-http-base)}))
+
+(rum/defc sync-server-url-settings-container
+  []
+  (let [current-url (config/get-custom-sync-server-url)
+        [url set-url!] (rum/use-state (or current-url ""))
+        reset-url! (fn []
+                     (config/set-custom-sync-server-url! nil)
+                     (set-url! "")
+                     (-> (push-sync-config-to-worker!)
+                         (p/then #(notification/show! (t :settings-page/sync-server-url-cleared) :success))
+                         (p/catch #(notification/show! (str "Failed to update worker: " %) :error))))]
+    [:div.cp__settings-sync-server-cnt
+     [:h1.mb-2.text-2xl.font-bold (t :settings-page/sync-server-url)]
+     [:div.p-2
+      [:p.text-sm.opacity-70.mb-4 (t :settings-page/sync-server-url-desc)]
+      [:p
+       [:label
+        [:strong "URL"]
+        [:input.form-input.is-small
+         {:value url
+          :placeholder config/default-db-sync-http-base
+          :style {:width "100%"}
+          :on-change #(set-url! (util/evalue %))}]]]
+      [:p.pt-2.flex.gap-2
+       (shui/button
+        {:size :sm
+         :on-click (fn []
+                     (let [trimmed (string/trim url)]
+                       (if (string/blank? trimmed)
+                         (reset-url!)
+                         (if-not (config/valid-sync-server-url? trimmed)
+                           (notification/show! "URL must start with https:// or http://" :error)
+                           (do
+                             (config/set-custom-sync-server-url! trimmed)
+                             (-> (push-sync-config-to-worker!)
+                                 (p/then #(notification/show! (t :settings-page/sync-server-url-saved) :success))
+                                 (p/catch #(notification/show! (str "Failed to update worker: " %) :error))))))))}
+        (t :save))
+       (when (seq url)
+         (shui/button
+          {:size :sm
+           :variant :outline
+           :on-click (fn [] (reset-url!))}
+          (t :settings-page/sync-server-url-reset)))]]]))
+
+(rum/defc sync-server-url-button
+  []
+  (let [current-url (config/get-custom-sync-server-url)]
+    (ui/button [:span.flex.items-center
+                [:span.pr-1
+                 (if (seq current-url)
+                   current-url
+                   (t :settings-page/sync-server-url-default))]
+                (ui/icon "edit")]
+               :class "text-sm"
+               :on-click #(state/pub-event! [:go/sync-server-settings]))))
+
+(defn sync-server-url-row []
+  (row-with-button-action
+   {:left-label (t :settings-page/sync-server-url)
+    :action (sync-server-url-button)}))
+
 (rum/defc user-proxy-settings
   [{:keys [type protocol host port] :as agent-opts}]
   (ui/button [:span.flex.items-center
@@ -661,6 +731,7 @@
      (when (and (or util/mac? util/win32?) (util/electron?)) (app-auto-update-row t))
      (usage-diagnostics-row t instrument-disabled?)
      (when-not (mobile-util/native-platform?) (developer-mode-row t developer-mode?))
+     (sync-server-url-row)
      (when (util/electron?) (https-user-agent-row https-agent-opts))
      (when (util/electron?) (auto-chmod-row t))
      ;; (clear-cache-row t)
diff --git a/src/main/frontend/config.cljs b/src/main/frontend/config.cljs
index 34447b19b3..45e07c0a59 100644
--- a/src/main/frontend/config.cljs
+++ b/src/main/frontend/config.cljs
@@ -50,19 +50,70 @@
 (goog-define ENABLE-DB-SYNC-LOCAL false)
 (defonce db-sync-local? ENABLE-DB-SYNC-LOCAL)
 
-(defonce db-sync-ws-url
+(defonce default-db-sync-ws-url
   (if db-sync-local?
     "ws://127.0.0.1:8787/sync/%s"
     ;; "wss://api-staging.logseq.io/sync/%s"
     "wss://api.logseq.io/sync/%s"))
 
-(defonce db-sync-http-base
+(defonce default-db-sync-http-base
   (if db-sync-local?
     "http://127.0.0.1:8787"
     ;; "https://api-staging.logseq.io"
     "https://api.logseq.io"
     ))
 
+(defn get-custom-sync-server-url
+  "Read the user-configured custom sync server URL from localStorage.
+   Returns nil when not set or empty."
+  []
+  (when-not util/node-test?
+    (let [v (.getItem js/localStorage "sync-server-url")]
+      (when (and (string? v) (not (string/blank? v)))
+        v))))
+
+(defn set-custom-sync-server-url!
+  "Persist the custom sync server URL to localStorage. Pass nil or empty string to clear."
+  [url]
+  (when-not util/node-test?
+    (if (or (nil? url) (string/blank? url))
+      (.removeItem js/localStorage "sync-server-url")
+      (.setItem js/localStorage "sync-server-url" (string/trim url)))))
+
+(defn valid-sync-server-url?
+  "Return true when `url` looks like a valid HTTP(S) base URL."
+  [url]
+  (and (string? url)
+       (re-find #"^https?://" url)))
+
+(defn custom-url->ws-url
+  "Derive a WebSocket sync URL from a custom HTTP base URL. Pure function."
+  [custom-url]
+  (let [scheme (if (string/starts-with? custom-url "https") "wss" "ws")
+        base (-> custom-url
+                 (string/replace #"^https?://" "")
+                 (string/replace #"/+$" ""))]
+    (str scheme "://" base "/sync/%s")))
+
+(defn custom-url->http-base
+  "Normalize a custom HTTP base URL by stripping trailing slashes. Pure function."
+  [custom-url]
+  (string/replace custom-url #"/+$" ""))
+
+(defn db-sync-ws-url
+  "Return the WebSocket sync URL. Uses custom server when configured, otherwise the default."
+  []
+  (if-let [custom (get-custom-sync-server-url)]
+    (custom-url->ws-url custom)
+    default-db-sync-ws-url))
+
+(defn db-sync-http-base
+  "Return the HTTP base URL for sync. Uses custom server when configured, otherwise the default."
+  []
+  (if-let [custom (get-custom-sync-server-url)]
+    (custom-url->http-base custom)
+    default-db-sync-http-base))
+
 ;; Feature flags
 ;; =============
 
diff --git a/src/main/frontend/handler/db_based/sync.cljs b/src/main/frontend/handler/db_based/sync.cljs
index b089dcd5e2..2b8959f642 100644
--- a/src/main/frontend/handler/db_based/sync.cljs
+++ b/src/main/frontend/handler/db_based/sync.cljs
@@ -28,8 +28,8 @@
       base)))
 
 (defn http-base []
-  (or config/db-sync-http-base
-      (ws->http-base config/db-sync-ws-url)))
+  (or (config/db-sync-http-base)
+      (ws->http-base (config/db-sync-ws-url))))
 
 (defn- auth-headers []
   (when-let [token (state/get-auth-id-token)]
diff --git a/src/main/frontend/handler/events/ui.cljs b/src/main/frontend/handler/events/ui.cljs
index 7e09902d6c..eca6c85d17 100644
--- a/src/main/frontend/handler/events/ui.cljs
+++ b/src/main/frontend/handler/events/ui.cljs
@@ -81,6 +81,11 @@
    (plugin/user-proxy-settings-container agent-opts)
    {:id :https-proxy-panel :center? true :class "lg:max-w-2xl"}))
 
+(defmethod events/handle :go/sync-server-settings [[_]]
+  (shui/dialog-open!
+   (settings/sync-server-url-settings-container)
+   {:id :sync-server-panel :center? true :class "lg:max-w-2xl"}))
+
 (defmethod events/handle :redirect-to-home [_]
   (page-handler/create-today-journal!)
   (when (util/capacitor?)
@@ -330,8 +335,8 @@
          (state/pub-event! [:rtc/sync-app-state])
          (state/<invoke-db-worker :thread-api/set-db-sync-config
                                   {:enabled? true
-                                   :ws-url config/db-sync-ws-url
-                                   :http-base config/db-sync-http-base})
+                                   :ws-url (config/db-sync-ws-url)
+                                   :http-base (config/db-sync-http-base)})
          (state/<invoke-db-worker :thread-api/db-sync-ensure-user-rsa-keys))
         (p/catch (fn [error]
                    (log/error :db-sync/ensure-user-rsa-keys-failed error)
diff --git a/src/main/frontend/handler/user.cljs b/src/main/frontend/handler/user.cljs
index 214814728e..71d9be6a0d 100644
--- a/src/main/frontend/handler/user.cljs
+++ b/src/main/frontend/handler/user.cljs
@@ -322,7 +322,8 @@
 
 (defn rtc-group?
   []
-  (boolean (seq (set/intersection (state/user-groups) #{"team" "rtc_2025_07_10"}))))
+  (boolean (or (some? (config/get-custom-sync-server-url))
+               (seq (set/intersection (state/user-groups) #{"team" "rtc_2025_07_10"})))))
 
 (defn alpha-user?
   []
diff --git a/src/main/frontend/persist_db/browser.cljs b/src/main/frontend/persist_db/browser.cljs
index 75acdabf72..9028cc02c4 100644
--- a/src/main/frontend/persist_db/browser.cljs
+++ b/src/main/frontend/persist_db/browser.cljs
@@ -129,8 +129,8 @@
        (-> (p/let [_ (state/<invoke-db-worker :thread-api/init)
                    _ (state/<invoke-db-worker :thread-api/set-db-sync-config
                                               {:enabled? true
-                                               :ws-url config/db-sync-ws-url
-                                               :http-base config/db-sync-http-base})
+                                               :ws-url (config/db-sync-ws-url)
+                                               :http-base (config/db-sync-http-base)})
                    _ (state/pub-event! [:rtc/sync-app-state])
                    _ (log/info "init worker spent" (str (- (util/time-ms) t1) "ms"))
                    _ (sync-ui-state!)
diff --git a/src/main/frontend/spec/storage.cljc b/src/main/frontend/spec/storage.cljc
index 4554ca1c74..41d97d7913 100644
--- a/src/main/frontend/spec/storage.cljc
+++ b/src/main/frontend/spec/storage.cljc
@@ -28,6 +28,7 @@
 (s/def :copy/export-block-text-indent-style string?)
 (s/def :copy/export-block-text-remove-options set?)
 (s/def :copy/export-block-text-other-options map?)
+(s/def ::sync-server-url string?)
 ;; Dynamic keys which aren't as easily validated:
 ;; :ls-pdf-last-page-*
 ;; :ls-js-allowed-*
@@ -66,4 +67,5 @@
             :ui/shortcut-tooltip?
             :copy/export-block-text-indent-style
             :copy/export-block-text-remove-options
-            :copy/export-block-text-other-options]))
+            :copy/export-block-text-other-options
+            ::sync-server-url]))
diff --git a/src/main/mobile/components/settings.cljs b/src/main/mobile/components/settings.cljs
index e73d3e60fa..d7b2af43e2 100644
--- a/src/main/mobile/components/settings.cljs
+++ b/src/main/mobile/components/settings.cljs
@@ -142,6 +142,14 @@
                     (shui/popup-show! nil (fn [] (log)) {}))}
        [:span.text-base "Check log"]]
 
+      [:div.mobile-setting-item
+       {:on-click #(state/pub-event! [:go/sync-server-settings])}
+       [:span.text-base "Sync server URL"]
+       [:span.text-sm.opacity-70
+        (if-let [custom (config/get-custom-sync-server-url)]
+          custom
+          "Logseq Cloud (default)")]]
+
       (when login?
         [:div.mobile-setting-item
          {:on-click (fn []
diff --git a/src/resources/dicts/en.edn b/src/resources/dicts/en.edn
index e18489de15..94fbc476c9 100644
--- a/src/resources/dicts/en.edn
+++ b/src/resources/dicts/en.edn
@@ -222,6 +222,12 @@
  :settings-page/plugin-system "Plugins"
  :settings-page/enable-flashcards "Flashcards"
  :settings-page/network-proxy "Network proxy"
+ :settings-page/sync-server-url "Sync server URL"
+ :settings-page/sync-server-url-desc "Set a custom HTTPS sync server URL for self-hosted sync. Your Logseq authentication tokens will be sent to this server, so only use a trusted URL. Leave empty to use the official Logseq cloud."
+ :settings-page/sync-server-url-saved "Sync server URL saved."
+ :settings-page/sync-server-url-cleared "Sync server URL cleared. Using official Logseq cloud."
+ :settings-page/sync-server-url-default "Logseq Cloud (default)"
+ :settings-page/sync-server-url-reset "Reset to default"
  :settings-page/login-prompt "To access new features before anyone else you must be an Open Collective Sponsor or Backer of Logseq and therefore log in first."
  :settings-page/native-titlebar "Native title bar"
  :settings-page/native-titlebar-desc "Enables the native window title bar on Windows and Linux."
diff --git a/src/test/frontend/config_test.cljs b/src/test/frontend/config_test.cljs
new file mode 100644
index 0000000000..cb140631ae
--- /dev/null
+++ b/src/test/frontend/config_test.cljs
@@ -0,0 +1,67 @@
+(ns frontend.config-test
+  (:require [cljs.test :refer [deftest is testing]]
+            [frontend.config :as config]))
+
+(deftest custom-url->ws-url-test
+  (testing "https URL becomes wss"
+    (is (= "wss://my-server.example.com/sync/%s"
+           (config/custom-url->ws-url "https://my-server.example.com"))))
+
+  (testing "http URL becomes ws"
+    (is (= "ws://localhost:8787/sync/%s"
+           (config/custom-url->ws-url "http://localhost:8787"))))
+
+  (testing "trailing slashes are stripped"
+    (is (= "wss://my-server.example.com/sync/%s"
+           (config/custom-url->ws-url "https://my-server.example.com/")))
+    (is (= "wss://my-server.example.com/sync/%s"
+           (config/custom-url->ws-url "https://my-server.example.com///"))))
+
+  (testing "preserves port in URL"
+    (is (= "wss://example.com:3000/sync/%s"
+           (config/custom-url->ws-url "https://example.com:3000"))))
+
+  (testing "preserves subpath in host"
+    ;; Users should only provide a base URL, but verify trailing path doesn't break things
+    (is (= "wss://example.com/api/sync/%s"
+           (config/custom-url->ws-url "https://example.com/api")))))
+
+(deftest custom-url->http-base-test
+  (testing "returns URL as-is when no trailing slash"
+    (is (= "https://my-server.example.com"
+           (config/custom-url->http-base "https://my-server.example.com"))))
+
+  (testing "strips trailing slashes"
+    (is (= "https://my-server.example.com"
+           (config/custom-url->http-base "https://my-server.example.com/")))
+    (is (= "https://my-server.example.com"
+           (config/custom-url->http-base "https://my-server.example.com///"))))
+
+  (testing "preserves http scheme"
+    (is (= "http://localhost:8787"
+           (config/custom-url->http-base "http://localhost:8787"))))
+
+  (testing "preserves port"
+    (is (= "https://example.com:3000"
+           (config/custom-url->http-base "https://example.com:3000/")))))
+
+(deftest default-urls-are-returned-when-no-custom-url
+  (testing "db-sync-ws-url returns default when no custom URL is set"
+    ;; In test environment, node-test? is true so get-custom-sync-server-url
+    ;; always returns nil, meaning we always get the default
+    (is (string? (config/db-sync-ws-url)))
+    (is (= config/default-db-sync-ws-url (config/db-sync-ws-url))))
+
+  (testing "db-sync-http-base returns default when no custom URL is set"
+    (is (string? (config/db-sync-http-base)))
+    (is (= config/default-db-sync-http-base (config/db-sync-http-base)))))
+
+(deftest valid-sync-server-url?-test
+  (testing "accepts http and https URLs"
+    (is (config/valid-sync-server-url? "https://my-server.example.com"))
+    (is (config/valid-sync-server-url? "http://localhost:8787")))
+
+  (testing "rejects non-URL strings"
+    (is (not (config/valid-sync-server-url? "not a url")))
+    (is (not (config/valid-sync-server-url? "")))
+    (is (not (config/valid-sync-server-url? nil)))))