diff --git a/extension/extension-utils.js b/extension/extension-utils.js
--- a/extension/extension-utils.js
+++ b/extension/extension-utils.js
@@ -20,6 +20,9 @@
 var callbacks = {}; // TODO rename to "portCallbacks"?
 var runtimeCallbacks = {};
 
+let currentMessageSerial = 0;
+let pendingMessageReplyResolvers = {};
+
 var storage = (IS_FIREFOX ? chrome.storage.local : chrome.storage.sync);
 
 let firefoxVersionMatch = navigator.userAgent.match(/Firefox\/(\d+)/)
@@ -53,6 +56,19 @@
     port.postMessage(message);
 }
 
+function sendPortMessageWithReply(subsystem, event, payload)
+{
+    return new Promise((resolve, reject) => {
+        let message = payload || {};
+        message.subsystem = subsystem;
+        message.event = event;
+        message.serial = ++currentMessageSerial;
+        pendingMessageReplyResolvers[message.serial] = resolve;
+
+        port.postMessage(message);
+    });
+}
+
 // Callback is called with following arguments (in that order);
 // - The actual message data/payload
 // - Information about the sender of the message (including tab and frameId)
diff --git a/extension/extension.js b/extension/extension.js
--- a/extension/extension.js
+++ b/extension/extension.js
@@ -104,13 +104,25 @@
     port.onMessage.addListener(function (message) {
         var subsystem = message.subsystem;
         var action = message.action;
+        let replyToSerial = message.replyToSerial;
 
-        if (!subsystem || !action) {
+        if (!replyToSerial && (!subsystem || !action)) {
             return;
         }
 
         receivedMessageOnce = true;
 
+        if (replyToSerial === "number") {
+            let replyResolver = pendingMessageReplyResolvers[replyToSerial];
+            if (replyResolver) {
+                replyResolver(message.payload);
+                delete pendingMessageReplyResolvers[replyToSerial];
+            } else {
+                console.warn("There is no reply resolver for message with serial", replyToSerial);
+            }
+            return;
+        }
+
         if (callbacks[subsystem] && callbacks[subsystem][action]) {
             callbacks[subsystem][action](message.payload, action);
         } else {
diff --git a/host/abstractbrowserplugin.h b/host/abstractbrowserplugin.h
--- a/host/abstractbrowserplugin.h
+++ b/host/abstractbrowserplugin.h
@@ -58,6 +58,7 @@
     virtual bool onUnload();
 
     void sendData(const QString &action, const QJsonObject &payload = QJsonObject());
+    void sendReply(const QJsonObject &payload = QJsonObject());
     QDebug debug() const;
 
     QJsonObject settings() const;
@@ -69,4 +70,5 @@
     int m_protocolVersion;
     bool m_loaded = false;
 
+    int m_currentRequestSerial = 0;
 };
diff --git a/host/abstractbrowserplugin.cpp b/host/abstractbrowserplugin.cpp
--- a/host/abstractbrowserplugin.cpp
+++ b/host/abstractbrowserplugin.cpp
@@ -50,6 +50,21 @@
     Connection::self()->sendData(data);
 }
 
+void AbstractBrowserPlugin::sendReply(const QJsonObject &payload)
+{
+    Q_ASSERT(m_currentRequestSerial > 0);
+
+    QJsonObject data{
+        {QStringLiteral("replyToSerial"), m_currentRequestSerial},
+    };
+
+    if (!payload.isEmpty()) {
+        data.insert(QStringLiteral("payload"), payload);
+    }
+
+    Connection::self()->sendData(data);
+}
+
 bool AbstractBrowserPlugin::onLoad()
 {
     return true;
diff --git a/host/pluginmanager.cpp b/host/pluginmanager.cpp
--- a/host/pluginmanager.cpp
+++ b/host/pluginmanager.cpp
@@ -124,6 +124,12 @@
         return;
     }
 
+    const int requestSerial = json.value(QStringLiteral("serial")).toInt();
+    plugin->m_currentRequestSerial = requestSerial;
+
     //design question, should we have a JSON of subsystem, event, payload, or have all data at the root level?
     plugin->handleData(event, json);
+
+    // TODO would be cool to have a delayed reply kind of feature like QDBusContext
+    plugin->m_currentRequestSerial = 0;
 }