diff --git a/matrix_sdk/Cargo.toml b/matrix_sdk/Cargo.toml
index 805283fe..46372aa4 100644
--- a/matrix_sdk/Cargo.toml
+++ b/matrix_sdk/Cargo.toml
@@ -68,6 +68,7 @@ features = ["wasm-bindgen"]
 
 [dev-dependencies]
 async-trait = "0.1.40"
+async-std = { version = "1.6.5", features = ["unstable"] }
 dirs = "3.0.1"
 matrix-sdk-test = { version = "0.1.0", path = "../matrix_sdk_test" }
 tokio = { version = "0.2.22", features = ["rt-threaded", "macros"] }
diff --git a/matrix_sdk/examples/autojoin.rs b/matrix_sdk/examples/autojoin.rs
index ece720e7..2af9a61b 100644
--- a/matrix_sdk/examples/autojoin.rs
+++ b/matrix_sdk/examples/autojoin.rs
@@ -64,9 +64,7 @@ async fn login_and_sync(
         .add_event_emitter(Box::new(AutoJoinBot::new(client.clone())))
         .await;
 
-    client
-        .sync_forever(SyncSettings::default(), |_| async {})
-        .await;
+    client.sync(SyncSettings::default()).await;
 
     Ok(())
 }
diff --git a/matrix_sdk/examples/command_bot.rs b/matrix_sdk/examples/command_bot.rs
index 9668b366..4f2d9fea 100644
--- a/matrix_sdk/examples/command_bot.rs
+++ b/matrix_sdk/examples/command_bot.rs
@@ -13,7 +13,7 @@ use url::Url;
 
 struct CommandBot {
     /// This clone of the `Client` will send requests to the server,
-    /// while the other keeps us in sync with the server using `sync_forever`.
+    /// while the other keeps us in sync with the server using `sync`.
     client: Client,
 }
 
@@ -91,18 +91,18 @@ async fn login_and_sync(
     // An initial sync to set up state and so our bot doesn't respond to old messages.
     // If the `StateStore` finds saved state in the location given the initial sync will
     // be skipped in favor of loading state from the store
-    client.sync(SyncSettings::default()).await.unwrap();
+    client.sync_once(SyncSettings::default()).await.unwrap();
     // add our CommandBot to be notified of incoming messages, we do this after the initial
     // sync to avoid responding to messages before the bot was running.
     client
         .add_event_emitter(Box::new(CommandBot::new(client.clone())))
         .await;
 
-    // since we called sync before we `sync_forever` we must pass that sync token to
-    // `sync_forever`
+    // since we called `sync_once` before we entered our sync loop we must pass
+    // that sync token to `sync`
     let settings = SyncSettings::default().token(client.sync_token().await.unwrap());
     // this keeps state from the server streaming in to CommandBot via the EventEmitter trait
-    client.sync_forever(settings, |_| async {}).await;
+    client.sync(settings).await;
 
     Ok(())
 }
diff --git a/matrix_sdk/examples/emoji_verification.rs b/matrix_sdk/examples/emoji_verification.rs
index 4b05d9c3..509e7ea4 100644
--- a/matrix_sdk/examples/emoji_verification.rs
+++ b/matrix_sdk/examples/emoji_verification.rs
@@ -2,7 +2,8 @@ use std::{env, io, process::exit};
 use url::Url;
 
 use matrix_sdk::{
-    self, events::AnyToDeviceEvent, identifiers::UserId, Client, ClientConfig, Sas, SyncSettings,
+    self, events::AnyToDeviceEvent, identifiers::UserId, Client, ClientConfig, LoopCtrl, Sas,
+    SyncSettings,
 };
 
 async fn wait_for_confirmation(client: Client, sas: Sas) {
@@ -69,7 +70,7 @@ async fn login(
     let client_ref = &client;
 
     client
-        .sync_forever(SyncSettings::new(), |response| async move {
+        .sync_with_callback(SyncSettings::new(), |response| async move {
             let client = &client_ref;
 
             for event in &response.to_device.events {
@@ -116,6 +117,8 @@ async fn login(
                     _ => (),
                 }
             }
+
+            LoopCtrl::Continue
         })
         .await;
 
diff --git a/matrix_sdk/examples/image_bot.rs b/matrix_sdk/examples/image_bot.rs
index 9479545c..68099d89 100644
--- a/matrix_sdk/examples/image_bot.rs
+++ b/matrix_sdk/examples/image_bot.rs
@@ -81,13 +81,13 @@ async fn login_and_sync(
         .login(&username, &password, None, Some("command bot"))
         .await?;
 
-    client.sync(SyncSettings::default()).await.unwrap();
+    client.sync_once(SyncSettings::default()).await.unwrap();
     client
         .add_event_emitter(Box::new(ImageBot::new(client.clone(), image)))
         .await;
 
     let settings = SyncSettings::default().token(client.sync_token().await.unwrap());
-    client.sync_forever(settings, |_| async {}).await;
+    client.sync(settings).await;
 
     Ok(())
 }
diff --git a/matrix_sdk/examples/login.rs b/matrix_sdk/examples/login.rs
index 875a3ee9..b63155b5 100644
--- a/matrix_sdk/examples/login.rs
+++ b/matrix_sdk/examples/login.rs
@@ -52,7 +52,7 @@ async fn login(
     client
         .login(username, password, None, Some("rust-sdk"))
         .await?;
-    client.sync_forever(SyncSettings::new(), |_| async {}).await;
+    client.sync(SyncSettings::new()).await;
 
     Ok(())
 }
diff --git a/matrix_sdk/examples/wasm_command_bot/src/lib.rs b/matrix_sdk/examples/wasm_command_bot/src/lib.rs
index a62f3b95..500736cf 100644
--- a/matrix_sdk/examples/wasm_command_bot/src/lib.rs
+++ b/matrix_sdk/examples/wasm_command_bot/src/lib.rs
@@ -7,7 +7,7 @@ use matrix_sdk::{
         AnyMessageEventContent, AnySyncMessageEvent, AnySyncRoomEvent, SyncMessageEvent,
     },
     identifiers::RoomId,
-    Client, ClientConfig, SyncSettings,
+    Client, ClientConfig, LoopCtrl, SyncSettings,
 };
 use url::Url;
 use wasm_bindgen::prelude::*;
@@ -41,7 +41,7 @@ impl WasmBot {
             self.0.room_send(&room_id, content, None).await.unwrap();
         }
     }
-    async fn on_sync_response(&self, response: SyncResponse) {
+    async fn on_sync_response(&self, response: SyncResponse) -> LoopCtrl {
         console::log_1(&"Synced".to_string().into());
 
         for (room_id, room) in response.rooms.join {
@@ -53,6 +53,8 @@ impl WasmBot {
                 }
             }
         }
+
+        LoopCtrl::Continue
     }
 }
 
@@ -73,11 +75,11 @@ pub async fn run() -> Result<JsValue, JsValue> {
 
     let bot = WasmBot(client.clone());
 
-    client.sync(SyncSettings::default()).await.unwrap();
+    client.sync_once(SyncSettings::default()).await.unwrap();
 
     let settings = SyncSettings::default().token(client.sync_token().await.unwrap());
     client
-        .sync_forever(settings, |response| bot.on_sync_response(response))
+        .sync_with_callback(settings, |response| bot.on_sync_response(response))
         .await;
 
     Ok(JsValue::NULL)
diff --git a/matrix_sdk/src/client.rs b/matrix_sdk/src/client.rs
index 6feaa40c..9d224765 100644
--- a/matrix_sdk/src/client.rs
+++ b/matrix_sdk/src/client.rs
@@ -47,6 +47,20 @@ use matrix_sdk_base::crypto::{
     AttachmentEncryptor, OutgoingRequests, ToDeviceRequest,
 };
 
+/// Enum controlling if a loop running callbacks should continue or abort.
+///
+/// This is mainly used in the [`sync_with_callback`] method, the return value
+/// of the provided callback controls if the sync loop should be exited.
+///
+/// [`sync_with_callback`]: #method.sync_with_callback
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LoopCtrl {
+    /// Continue running the loop.
+    Continue,
+    /// Break out of the loop.
+    Break,
+}
+
 use matrix_sdk_common::{
     api::r0::{
         account::register,
@@ -477,7 +491,7 @@ impl Client {
     /// If this isn't the first login a device id should be provided to restore
     /// the correct stores.
     ///
-    /// Alternatively the `restore_login()` method can be used to restore a
+    /// Alternatively the [`restore_login`] method can be used to restore a
     /// logged in client without the password.
     ///
     /// # Arguments
@@ -490,6 +504,29 @@ impl Client {
     ///     not given the homeserver will create one. Can be an existing
     ///     device_id from a previous login call. Note that this should be done
     ///     only if the client also holds the encryption keys for this device.
+    ///
+    /// # Example
+    /// ```no_run
+    /// # use std::convert::TryFrom;
+    /// # use matrix_sdk::Client;
+    /// # use matrix_sdk::identifiers::DeviceId;
+    /// # use matrix_sdk_common::assign;
+    /// # use futures::executor::block_on;
+    /// # use url::Url;
+    /// # let homeserver = Url::parse("http://example.com").unwrap();
+    /// # block_on(async {
+    /// let client = Client::new(homeserver).unwrap();
+    /// let user = "example";
+    /// let response = client
+    ///     .login(user, "wordpass", None, Some("My bot")).await
+    ///     .unwrap();
+    ///
+    /// println!("Logged in as {}, got device_id {} and access_token {}",
+    ///          user, response.device_id, response.access_token);
+    /// # })
+    /// ```
+    ///
+    /// [`restore_login`]: #method.restore_login
     #[instrument(skip(password))]
     pub async fn login(
         &self,
@@ -521,13 +558,15 @@ impl Client {
     /// This can be used to restore the client to a logged in state, loading all
     /// the stored state and encryption keys.
     ///
-    /// Alternatively, if the whole session isn't stored the `login()` method
+    /// Alternatively, if the whole session isn't stored the [`login`] method
     /// can be used with a device id.
     ///
     /// # Arguments
     ///
     /// * `session` - A session that the user already has from a
     /// previous login call.
+    ///
+    /// [`login`]: #method.login
     pub async fn restore_login(&self, session: Session) -> Result<()> {
         Ok(self.base_client.restore_login(session).await?)
     }
@@ -1342,14 +1381,20 @@ impl Client {
 
     /// Synchronize the client's state with the latest state on the server.
     ///
-    /// If a `StateStore` is provided and this is the initial sync state will
-    /// be loaded from the state store.
+    /// **Note**: You should not use this method to repeatedly sync if encryption
+    /// support is enabled, the [`sync`] method will make additional
+    /// requests between syncs that are needed for E2E encryption to work.
     ///
     /// # Arguments
     ///
     /// * `sync_settings` - Settings for the sync call.
+    ///
+    /// [`sync`]: #method.sync
     #[instrument]
-    pub async fn sync(&self, sync_settings: SyncSettings<'_>) -> Result<sync_events::Response> {
+    pub async fn sync_once(
+        &self,
+        sync_settings: SyncSettings<'_>,
+    ) -> Result<sync_events::Response> {
         let request = assign!(sync_events::Request::new(), {
             filter: sync_settings.filter,
             since: sync_settings.token.as_deref(),
@@ -1367,6 +1412,23 @@ impl Client {
         Ok(response)
     }
 
+    /// Repeatedly call sync to synchronize the client state with the server.
+    ///
+    /// This method will never return, if cancellation is needed the method
+    /// should be wrapped in a cancelable task or the [`sync_with_callback`]
+    /// method can be used.
+    ///
+    /// # Arguments
+    ///
+    /// * `sync_settings` - Settings for the sync call. Note that those settings
+    ///     will be only used for the first sync call.
+    ///
+    /// [`sync_with_callback`]: #method.sync_with_callback
+    pub async fn sync(&self, sync_settings: SyncSettings<'_>) {
+        self.sync_with_callback(sync_settings, |_| async { LoopCtrl::Continue })
+            .await
+    }
+
     /// Repeatedly call sync to synchronize the client state with the server.
     ///
     /// # Arguments
@@ -1375,7 +1437,10 @@ impl Client {
     ///     will be only used for the first sync call.
     ///
     /// * `callback` - A callback that will be called every time a successful
-    ///     response has been fetched from the server.
+    ///     response has been fetched from the server. The callback must return
+    ///     a boolean which signalizes if the method should stop syncing. If the
+    ///     callback returns `false` the sync will continue, if the callback
+    ///     returns `true` the sync will be stopped.
     ///
     /// # Examples
     ///
@@ -1385,18 +1450,17 @@ impl Client {
     ///
     /// ```compile_fail,E0658
     /// # use matrix_sdk::events::{
-    /// #     collections::all::RoomEvent,
     /// #     room::message::{MessageEvent, MessageEventContent, TextMessageEventContent},
-    /// #     EventResult,
     /// # };
     /// # use matrix_sdk::Room;
     /// # use std::sync::{Arc, RwLock};
-    /// # use matrix_sdk::{Client, SyncSettings};
+    /// # use std::time::Duration;
+    /// # use matrix_sdk::{Client, SyncSettings, LoopCtrl};
     /// # use url::Url;
     /// # use futures::executor::block_on;
     /// # block_on(async {
     /// # let homeserver = Url::parse("http://localhost:8080").unwrap();
-    /// # let mut client = Client::new(homeserver, None).unwrap();
+    /// # let mut client = Client::new(homeserver).unwrap();
     ///
     /// use async_std::sync::channel;
     ///
@@ -1404,31 +1468,32 @@ impl Client {
     ///
     /// let sync_channel = &tx;
     /// let sync_settings = SyncSettings::new()
-    ///     .timeout(30_000)
-    ///     .unwrap();
+    ///     .timeout(Duration::from_secs(30));
     ///
     /// client
-    ///     .sync_forever(sync_settings, async move |response| {
+    ///     .sync_with_callback(sync_settings, async move |response| {
     ///         let channel = sync_channel;
     ///
     ///         for (room_id, room) in response.rooms.join {
     ///             for event in room.timeline.events {
-    ///                 if let EventResult::Ok(e) = event {
+    ///                 if let Ok(e) = event.deserialize() {
     ///                     channel.send(e).await;
     ///                 }
     ///             }
     ///         }
+    ///
+    ///         LoopCtrl::Continue
     ///     })
     ///     .await;
     /// })
     /// ```
     #[instrument(skip(callback))]
-    pub async fn sync_forever<C>(
+    pub async fn sync_with_callback<C>(
         &self,
         sync_settings: SyncSettings<'_>,
         callback: impl Fn(sync_events::Response) -> C,
     ) where
-        C: Future<Output = ()>,
+        C: Future<Output = LoopCtrl>,
     {
         let mut sync_settings = sync_settings;
         let filter = sync_settings.filter;
@@ -1439,7 +1504,7 @@ impl Client {
         }
 
         loop {
-            let response = self.sync(sync_settings.clone()).await;
+            let response = self.sync_once(sync_settings.clone()).await;
 
             let response = match response {
                 Ok(r) => r,
@@ -1479,7 +1544,9 @@ impl Client {
                 }
             }
 
-            callback(response).await;
+            if callback(response).await == LoopCtrl::Break {
+                return;
+            }
 
             let now = Instant::now();
 
@@ -1766,7 +1833,10 @@ impl Client {
     /// ```
     #[cfg(feature = "encryption")]
     #[cfg(not(target_arch = "wasm32"))]
-    #[cfg_attr(feature = "docs", doc(cfg(encryption)))]
+    #[cfg_attr(
+        feature = "docs",
+        doc(cfg(all(encryption, not(target_arch = "wasm32"))))
+    )]
     pub async fn export_keys(
         &self,
         path: PathBuf,
@@ -1816,7 +1886,10 @@ impl Client {
     /// ```
     #[cfg(feature = "encryption")]
     #[cfg(not(target_arch = "wasm32"))]
-    #[cfg_attr(feature = "docs", doc(cfg(encryption)))]
+    #[cfg_attr(
+        feature = "docs",
+        doc(cfg(all(encryption, not(target_arch = "wasm32"))))
+    )]
     pub async fn import_keys(&self, path: PathBuf, passphrase: &str) -> Result<()> {
         let olm = self
             .base_client
@@ -1944,7 +2017,7 @@ mod test {
         let room = client.get_joined_room(&room_id).await;
         assert!(room.is_none());
 
-        client.sync(SyncSettings::default()).await.unwrap();
+        client.sync_once(SyncSettings::default()).await.unwrap();
 
         let room = client.get_left_room(&room_id).await;
         assert!(room.is_none());
@@ -1959,7 +2032,10 @@ mod test {
         joined_client.restore_login(session).await.unwrap();
 
         // joined room reloaded from state store
-        joined_client.sync(SyncSettings::default()).await.unwrap();
+        joined_client
+            .sync_once(SyncSettings::default())
+            .await
+            .unwrap();
         let room = joined_client.get_joined_room(&room_id).await;
         assert!(room.is_some());
 
@@ -1971,7 +2047,10 @@ mod test {
         .with_body(test_json::LEAVE_SYNC_EVENT.to_string())
         .create();
 
-        joined_client.sync(SyncSettings::default()).await.unwrap();
+        joined_client
+            .sync_once(SyncSettings::default())
+            .await
+            .unwrap();
 
         let room = joined_client.get_joined_room(&room_id).await;
         assert!(room.is_none());
@@ -1994,7 +2073,7 @@ mod test {
         .create();
 
         let sync_settings = SyncSettings::new().timeout(Duration::from_millis(3000));
-        let _response = client.sync(sync_settings).await.unwrap();
+        let _response = client.sync_once(sync_settings).await.unwrap();
 
         // let bc = &client.base_client;
         // let ignored_users = bc.ignored_users.read().await;
@@ -2463,7 +2542,7 @@ mod test {
 
         let sync_settings = SyncSettings::new().timeout(Duration::from_millis(3000));
 
-        let _response = client.sync(sync_settings).await.unwrap();
+        let _response = client.sync_once(sync_settings).await.unwrap();
 
         let rooms_lock = &client.base_client.joined_rooms();
         let rooms = rooms_lock.read().await;
@@ -2491,7 +2570,7 @@ mod test {
         .create();
 
         let sync_settings = SyncSettings::new().timeout(Duration::from_millis(3000));
-        let _response = client.sync(sync_settings).await.unwrap();
+        let _response = client.sync_once(sync_settings).await.unwrap();
 
         let mut room_names = vec![];
         for room in client.joined_rooms().read().await.values() {
@@ -2514,7 +2593,7 @@ mod test {
         .with_body(test_json::INVITE_SYNC.to_string())
         .create();
 
-        let _response = client.sync(SyncSettings::default()).await.unwrap();
+        let _response = client.sync_once(SyncSettings::default()).await.unwrap();
 
         assert!(client.joined_rooms().read().await.is_empty());
         assert!(client.left_rooms().read().await.is_empty());
@@ -2539,7 +2618,7 @@ mod test {
         .with_body(test_json::LEAVE_SYNC.to_string())
         .create();
 
-        let _response = client.sync(SyncSettings::default()).await.unwrap();
+        let _response = client.sync_once(SyncSettings::default()).await.unwrap();
 
         assert!(client.joined_rooms().read().await.is_empty());
         assert!(!client.left_rooms().read().await.is_empty());
@@ -2583,14 +2662,14 @@ mod test {
         let sync_settings = SyncSettings::new().timeout(std::time::Duration::from_millis(3000));
 
         // gather state to save to the db, the first time through loading will be skipped
-        let _ = client.sync(sync_settings.clone()).await.unwrap();
+        let _ = client.sync_once(sync_settings.clone()).await.unwrap();
 
         // now syncing the client will update from the state store
         let config =
             ClientConfig::default().state_store(Box::new(JsonStore::open(dir.path()).unwrap()));
         let client = Client::new_with_config(homeserver, config).unwrap();
         client.restore_login(session.clone()).await.unwrap();
-        client.sync(sync_settings).await.unwrap();
+        client.sync_once(sync_settings).await.unwrap();
 
         let base_client = &client.base_client;
 
@@ -2623,7 +2702,7 @@ mod test {
 
         let sync_settings = SyncSettings::new().timeout(Duration::from_millis(3000));
 
-        let response = client.sync(sync_settings).await.unwrap();
+        let response = client.sync_once(sync_settings).await.unwrap();
 
         assert_ne!(response.next_batch, "");
 
@@ -2645,7 +2724,7 @@ mod test {
 
         let sync_settings = SyncSettings::new().timeout(Duration::from_millis(3000));
 
-        let _response = client.sync(sync_settings).await.unwrap();
+        let _response = client.sync_once(sync_settings).await.unwrap();
 
         let mut names = vec![];
         for r in client.joined_rooms().read().await.values() {
diff --git a/matrix_sdk/src/lib.rs b/matrix_sdk/src/lib.rs
index 3dd243b5..078de2e1 100644
--- a/matrix_sdk/src/lib.rs
+++ b/matrix_sdk/src/lib.rs
@@ -71,7 +71,7 @@ mod device;
 #[cfg(feature = "encryption")]
 mod sas;
 
-pub use client::{Client, ClientConfig, SyncSettings};
+pub use client::{Client, ClientConfig, LoopCtrl, SyncSettings};
 #[cfg(feature = "encryption")]
 #[cfg_attr(feature = "docs", doc(cfg(encryption)))]
 pub use device::Device;