diff --git a/spec/integ/sliding-sync-sdk.spec.ts b/spec/integ/sliding-sync-sdk.spec.ts
index 3a43f9e12..72a7eeaa2 100644
--- a/spec/integ/sliding-sync-sdk.spec.ts
+++ b/spec/integ/sliding-sync-sdk.spec.ts
@@ -928,4 +928,90 @@ describe("SlidingSyncSdk", () => {
             expect(room.getMember(selfUserId)?.typing).toEqual(false);
         });
     });
+
+    describe("ExtensionReceipts", () => {
+        let ext: Extension;
+
+        const generateReceiptResponse = (
+            userId: string, roomId: string, eventId: string, recType: string, ts: number,
+        ) => {
+            return {
+                rooms: {
+                    [roomId]: {
+                        type: EventType.Receipt,
+                        content: {
+                            [eventId]: {
+                                [recType]: {
+                                    [userId]: {
+                                        ts: ts,
+                                    },
+                                },
+                            },
+                        },
+                    },
+                },
+            };
+        };
+
+        beforeAll(async () => {
+            await setupClient();
+            const hasSynced = sdk!.sync();
+            await httpBackend!.flushAllExpected();
+            await hasSynced;
+            ext = findExtension("receipts");
+        });
+
+        it("gets enabled on the initial request only", () => {
+            expect(ext.onRequest(true)).toEqual({
+                enabled: true,
+            });
+            expect(ext.onRequest(false)).toEqual(undefined);
+        });
+
+        it("processes receipts", async () => {
+            const roomId = "!room:id";
+            const alice = "@alice:alice";
+            const lastEvent = mkOwnEvent(EventType.RoomMessage, { body: "hello" });
+            mockSlidingSync!.emit(SlidingSyncEvent.RoomData, roomId, {
+                name: "Room with receipts",
+                required_state: [],
+                timeline: [
+                    mkOwnStateEvent(EventType.RoomCreate, { creator: selfUserId }, ""),
+                    mkOwnStateEvent(EventType.RoomMember, { membership: "join" }, selfUserId),
+                    mkOwnStateEvent(EventType.RoomPowerLevels, { users: { [selfUserId]: 100 } }, ""),
+                    {
+                        type: EventType.RoomMember,
+                        state_key: alice,
+                        content: { membership: "join" },
+                        sender: alice,
+                        origin_server_ts: Date.now(),
+                        event_id: "$alice",
+                    },
+                    lastEvent,
+                ],
+                initial: true,
+            });
+            const room = client!.getRoom(roomId)!;
+            expect(room).toBeDefined();
+            expect(room.getReadReceiptForUserId(alice, true)).toBeNull();
+            ext.onResponse(
+                generateReceiptResponse(alice, roomId, lastEvent.event_id, "m.read", 1234567),
+            );
+            const receipt = room.getReadReceiptForUserId(alice);
+            expect(receipt).toBeDefined();
+            expect(receipt?.eventId).toEqual(lastEvent.event_id);
+            expect(receipt?.data.ts).toEqual(1234567);
+            expect(receipt?.data.thread_id).toBeFalsy();
+        });
+
+        it("gracefully handles missing rooms when receiving receipts", async () => {
+            const roomId = "!room:id";
+            const alice = "@alice:alice";
+            const eventId = "$something";
+            ext.onResponse(
+                generateReceiptResponse(alice, roomId, eventId, "m.read", 1234567),
+            );
+            // we expect it not to crash
+        });
+    });
 });
diff --git a/src/sliding-sync-sdk.ts b/src/sliding-sync-sdk.ts
index f12b51c65..a787b4e34 100644
--- a/src/sliding-sync-sdk.ts
+++ b/src/sliding-sync-sdk.ts
@@ -246,29 +246,55 @@ class ExtensionTyping implements Extension {
 
     public onRequest(isInitial: boolean): object | undefined {
         if (!isInitial) {
-            return undefined;
+            return undefined; // don't send a JSON object for subsequent requests, we don't need to.
         }
         return {
             enabled: true,
         };
     }
 
-    public onResponse(data: {rooms: Record<string, Event[]>}): void {
+    public onResponse(data: {rooms: Record<string, IMinimalEvent>}): void {
         if (!data || !data.rooms) {
             return;
         }
 
         for (const roomId in data.rooms) {
-            const ephemeralEvents = mapEvents(this.client, roomId, [data.rooms[roomId]]);
-            const room = this.client.getRoom(roomId);
-            if (!room) {
-                logger.warn("got typing events for room but room doesn't exist on client:", roomId);
-                continue;
-            }
-            room.addEphemeralEvents(ephemeralEvents);
-            ephemeralEvents.forEach((e) => {
-                this.client.emit(ClientEvent.Event, e);
-            });
+            processEphemeralEvents(
+                this.client, roomId, [data.rooms[roomId]],
+            );
+        }
+    }
+}
+
+class ExtensionReceipts implements Extension {
+    public constructor(private readonly client: MatrixClient) {}
+
+    public name(): string {
+        return "receipts";
+    }
+
+    public when(): ExtensionState {
+        return ExtensionState.PostProcess;
+    }
+
+    public onRequest(isInitial: boolean): object | undefined {
+        if (isInitial) {
+            return {
+                enabled: true,
+            };
+        }
+        return undefined; // don't send a JSON object for subsequent requests, we don't need to.
+    }
+
+    public onResponse(data: {rooms: Record<string, IMinimalEvent>}): void {
+        if (!data || !data.rooms) {
+            return;
+        }
+
+        for (const roomId in data.rooms) {
+            processEphemeralEvents(
+                this.client, roomId, [data.rooms[roomId]],
+            );
         }
     }
 }
@@ -314,6 +340,7 @@ export class SlidingSyncSdk {
             new ExtensionToDevice(this.client),
             new ExtensionAccountData(this.client),
             new ExtensionTyping(this.client),
+            new ExtensionReceipts(this.client),
         ];
         if (this.opts.crypto) {
             extensions.push(
@@ -929,3 +956,16 @@ function mapEvents(client: MatrixClient, roomId: string | undefined, events: obj
         return mapper(e);
     });
 }
+
+function processEphemeralEvents(client: MatrixClient, roomId: string, ephEvents: IMinimalEvent[]): void {
+    const ephemeralEvents = mapEvents(client, roomId, ephEvents);
+    const room = client.getRoom(roomId);
+    if (!room) {
+        logger.warn("got ephemeral events for room but room doesn't exist on client:", roomId);
+        return;
+    }
+    room.addEphemeralEvents(ephemeralEvents);
+    ephemeralEvents.forEach((e) => {
+        client.emit(ClientEvent.Event, e);
+    });
+}