diff --git a/briar-headless/README.md b/briar-headless/README.md
index 2acfdac3a..fbeb7c804 100644
--- a/briar-headless/README.md
+++ b/briar-headless/README.md
@@ -410,3 +410,39 @@ When the last connection is lost (the contact goes offline), it sends a `Contact
     "type": "event"
 }
 ```
+
+### A message was sent
+
+When Briar sent a message to a contact, it sends a `MessagesSentEvent`. This is indicated in Briar
+by showing one tick next to the message.
+
+```json
+{
+    "data": {
+        "contactId": 1,
+        "messageIds": [
+            "+AIMMgOCPFF8HDEhiEHYjbfKrg7v0G94inKxjvjYzA8="
+        ]
+    },
+    "name": "MessagesSentEvent",
+    "type": "event"
+}
+```
+
+### A message was acknowledged
+
+When a contact acknowledges that they received a message, Briar sends a `MessagesAckedEvent`.
+This is indicated in Briar by showing two ticks next to the message.
+
+```json
+{
+    "data": {
+        "contactId": 1,
+        "messageIds": [
+            "+AIMMgOCPFF8HDEhiEHYjbfKrg7v0G94inKxjvjYzA8="
+        ]
+    },
+    "name": "MessagesAckedEvent",
+    "type": "event"
+}
+```
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt
index d3ee6457e..df5607170 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt
@@ -11,6 +11,8 @@ import org.briarproject.bramble.api.db.DatabaseExecutor
 import org.briarproject.bramble.api.db.NoSuchContactException
 import org.briarproject.bramble.api.event.Event
 import org.briarproject.bramble.api.event.EventListener
+import org.briarproject.bramble.api.sync.event.MessagesAckedEvent
+import org.briarproject.bramble.api.sync.event.MessagesSentEvent
 import org.briarproject.bramble.api.system.Clock
 import org.briarproject.bramble.util.StringUtils.utf8IsTooLong
 import org.briarproject.briar.api.blog.BlogInvitationRequest
@@ -39,6 +41,8 @@ import javax.inject.Inject
 import javax.inject.Singleton
 
 internal const val EVENT_CONVERSATION_MESSAGE = "ConversationMessageReceivedEvent"
+internal const val EVENT_MESSAGES_ACKED = "MessagesAckedEvent"
+internal const val EVENT_MESSAGES_SENT = "MessagesSentEvent"
 
 @Immutable
 @Singleton
@@ -90,6 +94,12 @@ constructor(
                     webSocketController.sendEvent(EVENT_CONVERSATION_MESSAGE, e.output())
                 }
             }
+            is MessagesSentEvent -> {
+                webSocketController.sendEvent(EVENT_MESSAGES_SENT, e.output())
+            }
+            is MessagesAckedEvent -> {
+                webSocketController.sendEvent(EVENT_MESSAGES_ACKED, e.output())
+            }
         }
     }
 
diff --git a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputConversationMessage.kt b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputConversationMessage.kt
index ddd9c807c..3c42a39d0 100644
--- a/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputConversationMessage.kt
+++ b/briar-headless/src/main/java/org/briarproject/briar/headless/messaging/OutputConversationMessage.kt
@@ -1,6 +1,9 @@
 package org.briarproject.briar.headless.messaging
 
 import org.briarproject.bramble.api.contact.ContactId
+import org.briarproject.bramble.api.sync.MessageId
+import org.briarproject.bramble.api.sync.event.MessagesAckedEvent
+import org.briarproject.bramble.api.sync.event.MessagesSentEvent
 import org.briarproject.briar.api.conversation.ConversationMessageHeader
 import org.briarproject.briar.api.messaging.PrivateMessage
 import org.briarproject.briar.api.messaging.PrivateMessageHeader
@@ -43,3 +46,15 @@ internal fun PrivateMessage.output(contactId: ContactId, text: String) = JsonDic
     "groupId" to message.groupId.bytes,
     "text" to text
 )
+
+internal fun MessagesAckedEvent.output() = JsonDict(
+    "contactId" to contactId.int,
+    "messageIds" to messageIds.toJson()
+)
+
+internal fun MessagesSentEvent.output() = JsonDict(
+    "contactId" to contactId.int,
+    "messageIds" to messageIds.toJson()
+)
+
+internal fun Collection<MessageId>.toJson() = map { it.bytes }
diff --git a/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt b/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
index 4968f9849..6feac73e2 100644
--- a/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
+++ b/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
@@ -10,11 +10,13 @@ import org.briarproject.bramble.api.db.NoSuchContactException
 import org.briarproject.bramble.api.identity.AuthorInfo
 import org.briarproject.bramble.api.identity.AuthorInfo.Status.UNVERIFIED
 import org.briarproject.bramble.api.identity.AuthorInfo.Status.VERIFIED
+import org.briarproject.bramble.api.sync.MessageId
+import org.briarproject.bramble.api.sync.event.MessagesAckedEvent
+import org.briarproject.bramble.api.sync.event.MessagesSentEvent
 import org.briarproject.bramble.test.ImmediateExecutor
 import org.briarproject.bramble.test.TestUtils.getRandomId
 import org.briarproject.bramble.util.StringUtils.getRandomString
 import org.briarproject.briar.api.client.SessionId
-import org.briarproject.briar.api.conversation.ConversationManager
 import org.briarproject.briar.api.introduction.IntroductionRequest
 import org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_TEXT_LENGTH
 import org.briarproject.briar.api.messaging.MessagingManager
@@ -100,6 +102,40 @@ internal class MessagingControllerImplTest : ControllerTest() {
         testInvalidContactId { controller.list(ctx) }
     }
 
+    @Test
+    fun testMessagesAckedEvent() {
+        val messageId1 = MessageId(getRandomId())
+        val messageId2 = MessageId(getRandomId())
+        val messageIds = listOf(messageId1, messageId2)
+        val event = MessagesAckedEvent(contact.id, messageIds)
+
+        every {
+            webSocketController.sendEvent(
+                EVENT_MESSAGES_ACKED,
+                event.output()
+            )
+        } just runs
+
+        controller.eventOccurred(event)
+    }
+
+    @Test
+    fun testMessagesSentEvent() {
+        val messageId1 = MessageId(getRandomId())
+        val messageId2 = MessageId(getRandomId())
+        val messageIds = listOf(messageId1, messageId2)
+        val event = MessagesSentEvent(contact.id, messageIds)
+
+        every {
+            webSocketController.sendEvent(
+                EVENT_MESSAGES_SENT,
+                event.output()
+            )
+        } just runs
+
+        controller.eventOccurred(event)
+    }
+
     @Test
     fun listNonexistentContactId() {
         testNonexistentContactId { controller.list(ctx) }
@@ -177,6 +213,43 @@ internal class MessagingControllerImplTest : ControllerTest() {
         controller.eventOccurred(event)
     }
 
+    @Test
+    fun testOutputMessagesAckedEvent() {
+        val messageId1 = MessageId(getRandomId())
+        val messageId2 = MessageId(getRandomId())
+        val messageIds = listOf(messageId1, messageId2)
+        val event = MessagesAckedEvent(contact.id, messageIds)
+        val json = """
+            {
+                "contactId": ${contact.id.int},
+                "messageIds": [
+                    ${toJson(messageId1.bytes)},
+                    ${toJson(messageId2.bytes)}
+                ]
+            }
+        """
+        assertJsonEquals(json, event.output())
+    }
+
+    @Test
+    fun testOutputMessagesSentEvent() {
+        val messageId1 = MessageId(getRandomId())
+        val messageId2 = MessageId(getRandomId())
+        val messageIds = listOf(messageId1, messageId2)
+        val event = MessagesSentEvent(contact.id, messageIds)
+
+        val json = """
+            {
+                "contactId": ${contact.id.int},
+                "messageIds": [
+                    ${toJson(messageId1.bytes)},
+                    ${toJson(messageId2.bytes)}
+                ]
+            }
+        """
+        assertJsonEquals(json, event.output())
+    }
+
     @Test
     fun testOutputPrivateMessageHeader() {
         val json = """