diff --git a/backend/src/aurinko/registry.gleam b/backend/src/aurinko/registry.gleam
index 49dead5..a0bf833 100644
--- a/backend/src/aurinko/registry.gleam
+++ b/backend/src/aurinko/registry.gleam
@@ -1,26 +1,17 @@
 import chip
 import gleam/erlang/process
 import gleam/otp/actor
-import gleam/otp/supervisor
 
-pub type Id {
-  Updater
-}
+pub type Store(message, id) =
+  chip.Registry(message, id, Nil)
 
-pub type Store(message) =
-  chip.Registry(message, Id, Nil)
-
-pub fn start() -> Result(Store(message), actor.StartError) {
+pub fn start() -> Result(Store(message, id), actor.StartError) {
   chip.start()
 }
 
-pub fn childspec() {
-  supervisor.worker(fn(_index) { start() })
-}
-
 pub fn register(
-  store: Store(message),
-  id: Id,
+  store: Store(message, id),
+  id: id,
   subject: process.Subject(message),
 ) {
   chip.new(subject)
@@ -28,6 +19,6 @@ pub fn register(
   |> chip.register(store, _)
 }
 
-pub fn get(store: Store(message), id: Id) {
+pub fn get(store: Store(message, id), id: id) {
   chip.find(store, id)
 }
diff --git a/backend/src/aurinko/updater.gleam b/backend/src/aurinko/updater.gleam
index 5ef48fb..1643648 100644
--- a/backend/src/aurinko/updater.gleam
+++ b/backend/src/aurinko/updater.gleam
@@ -1,7 +1,10 @@
 import ap_systems/api
 import ap_systems/module_power
-import aurinko/registry
+import aurinko/updater/messaging.{
+  type Message, GetData, GetDataResponse, PeriodicUpdate, Update,
+}
 import aurinko/updater/pubsub
+import aurinko/updater/registry
 import aurinko/updater/types.{
   type Dataset, type ModuleDataset, Dataset, ModuleDataset, ModulePower,
 }
@@ -11,7 +14,6 @@ import biscotto
 import gleam/dict
 import gleam/dynamic
 import gleam/erlang/process
-import gleam/io
 import gleam/list
 import gleam/option
 import gleam/order
@@ -24,16 +26,6 @@ const update_interval = 30_000
 
 const login_cookie_expiry = 86_400
 
-pub type GetDataResponse {
-  GetDataResponse(dataset: option.Option(Dataset))
-}
-
-pub type Message {
-  Update
-  PeriodicUpdate
-  GetData(reply_subject: process.Subject(GetDataResponse))
-}
-
 pub type ModuleIDs =
   api.ModuleIDs
 
@@ -81,7 +73,7 @@ pub fn start(
   username: String,
   password: String,
   pubsub: pubsub.UpdaterPubSub,
-  updater_registry: registry.Store(Message),
+  updater_registry: registry.UpdaterRegistry,
 ) {
   let spec =
     actor.Spec(
@@ -91,7 +83,7 @@ pub fn start(
           process.new_selector() |> process.selecting(self_subject, fn(a) { a })
 
         registry.register(updater_registry, registry.Updater, self_subject)
-        process.send_after(self_subject, 0, PeriodicUpdate)
+        process.send_after(self_subject, 0, Update)
         process.send_after(self_subject, update_interval, PeriodicUpdate)
 
         actor.Ready(
@@ -147,8 +139,6 @@ fn handle_message(message: Message, state: State) -> actor.Next(Message, State)
       }
     })
 
-  io.debug(#("Next state", next))
-
   case next {
     Ok(next) -> next
     Error(err) -> {
diff --git a/backend/src/aurinko/updater/messaging.gleam b/backend/src/aurinko/updater/messaging.gleam
new file mode 100644
index 0000000..baa9bd9
--- /dev/null
+++ b/backend/src/aurinko/updater/messaging.gleam
@@ -0,0 +1,13 @@
+import aurinko/updater/types
+import gleam/erlang/process
+import gleam/option
+
+pub type GetDataResponse {
+  GetDataResponse(dataset: option.Option(types.Dataset))
+}
+
+pub type Message {
+  Update
+  PeriodicUpdate
+  GetData(reply_subject: process.Subject(GetDataResponse))
+}
diff --git a/backend/src/aurinko/updater/pubsub.gleam b/backend/src/aurinko/updater/pubsub.gleam
index 63d6ede..9372b1b 100644
--- a/backend/src/aurinko/updater/pubsub.gleam
+++ b/backend/src/aurinko/updater/pubsub.gleam
@@ -13,3 +13,5 @@ pub type UpdaterPubSub =
 pub fn init() -> actor.StartResult(glubsub.Message(OutMessage)) {
   generic_pubsub.init()
 }
+
+pub const from_subject = generic_pubsub.from_subject
diff --git a/backend/src/aurinko/updater/registry.gleam b/backend/src/aurinko/updater/registry.gleam
new file mode 100644
index 0000000..aa04260
--- /dev/null
+++ b/backend/src/aurinko/updater/registry.gleam
@@ -0,0 +1,20 @@
+import aurinko/registry
+import aurinko/updater/messaging
+import gleam/otp/actor
+
+pub type Id {
+  Updater
+}
+
+pub type UpdaterRegistry =
+  registry.Store(messaging.Message, Id)
+
+pub fn start() -> Result(UpdaterRegistry, actor.StartError) {
+  registry.start()
+}
+
+pub const register = registry.register
+
+pub fn get(updater_registry: UpdaterRegistry) {
+  registry.get(updater_registry, Updater)
+}
diff --git a/backend/src/aurinko/web.gleam b/backend/src/aurinko/web.gleam
index 7233f2f..85ce10d 100644
--- a/backend/src/aurinko/web.gleam
+++ b/backend/src/aurinko/web.gleam
@@ -1,8 +1,9 @@
-import aurinko/registry
-import aurinko/updater
 import aurinko/updater/pubsub
+import aurinko/updater/registry
 import aurinko/web/router
+import aurinko/web/ws
 import gleam/dynamic
+import gleam/http/request
 import gleam/otp/actor
 import gleam/result
 import mist
@@ -11,12 +12,25 @@ import wisp
 pub fn init(
   port: Int,
   secret_key_base: String,
-  _updater_pubsub: pubsub.UpdaterPubSub,
-  _updater_registry: registry.Store(updater.Message),
+  updater_pubsub: pubsub.UpdaterPubSub,
+  updater_registry: registry.UpdaterRegistry,
 ) {
   wisp.configure_logger()
 
-  wisp.mist_handler(router.handle_request, secret_key_base)
+  let wisp_side = wisp.mist_handler(router.handle_request, secret_key_base)
+
+  fn(req) {
+    case request.path_segments(req) {
+      ["ws"] ->
+        mist.websocket(
+          request: req,
+          on_init: ws.on_init(_, updater_pubsub, updater_registry),
+          on_close: ws.on_close,
+          handler: ws.handle_message,
+        )
+      _ -> wisp_side(req)
+    }
+  }
   |> mist.new()
   |> mist.port(port)
   |> mist.start_http()
diff --git a/backend/src/aurinko/web/ws.gleam b/backend/src/aurinko/web/ws.gleam
new file mode 100644
index 0000000..14cfea9
--- /dev/null
+++ b/backend/src/aurinko/web/ws.gleam
@@ -0,0 +1,89 @@
+import aurinko/updater
+import aurinko/updater/messaging
+import aurinko/updater/pubsub
+import aurinko/updater/registry
+import aurinko/web/ws/encoder
+import gleam/erlang/process
+import gleam/json
+import gleam/option
+import gleam/otp/actor
+import glubsub
+import mist
+
+pub type State {
+  State(
+    updater_pubsub: pubsub.UpdaterPubSub,
+    updater_registry: registry.UpdaterRegistry,
+    pubsub_subject: process.Subject(pubsub.OutMessage),
+  )
+}
+
+pub fn on_init(
+  conn: mist.WebsocketConnection,
+  updater_pubsub: pubsub.UpdaterPubSub,
+  updater_registry: registry.UpdaterRegistry,
+) {
+  let pubsub_subject = process.new_subject()
+  let assert Ok(_) = glubsub.subscribe(updater_pubsub, pubsub_subject)
+
+  send_initial_dataset(conn, updater_registry)
+
+  let self_selector =
+    process.new_selector() |> process.selecting(pubsub_subject, fn(m) { m })
+  let state = State(updater_pubsub, updater_registry, pubsub_subject)
+  #(state, option.Some(self_selector))
+}
+
+pub fn on_close(state: State) {
+  let _ = glubsub.unsubscribe(state.updater_pubsub, state.pubsub_subject)
+  Nil
+}
+
+pub fn handle_message(
+  state: State,
+  conn: mist.WebsocketConnection,
+  message: mist.WebsocketMessage(pubsub.OutMessage),
+) {
+  case message {
+    mist.Custom(pubsub.NewData(dataset)) -> {
+      let dataset = encoder.dataset(dataset)
+      let output =
+        json.object([
+          #("type", json.string("data_update")),
+          #("dataset", dataset),
+        ])
+        |> json.to_string()
+      let assert Ok(_) = mist.send_text_frame(conn, output)
+      actor.continue(state)
+    }
+    mist.Closed | mist.Shutdown -> actor.Stop(process.Normal)
+    _ -> actor.continue(state)
+  }
+}
+
+fn send_initial_dataset(
+  conn: mist.WebsocketConnection,
+  updater_registry: registry.UpdaterRegistry,
+) {
+  let updater_subject = registry.get(updater_registry)
+  case updater_subject {
+    Ok(sub) -> {
+      let messaging.GetDataResponse(initial_data) = updater.get_data(sub)
+      let dataset = case initial_data {
+        option.Some(dataset) -> encoder.dataset(dataset)
+        option.None -> json.null()
+      }
+
+      let output =
+        json.object([
+          #("type", json.string("initial_data")),
+          #("dataset", dataset),
+        ])
+        |> json.to_string()
+
+      let assert Ok(_) = mist.send_text_frame(conn, output)
+      Nil
+    }
+    Error(_) -> Nil
+  }
+}
diff --git a/backend/src/aurinko/web/ws/encoder.gleam b/backend/src/aurinko/web/ws/encoder.gleam
new file mode 100644
index 0000000..cdb82af
--- /dev/null
+++ b/backend/src/aurinko/web/ws/encoder.gleam
@@ -0,0 +1,72 @@
+import ap_systems/module_power
+import aurinko/updater/types
+import birl
+import gleam/dict
+import gleam/json
+import gleam/list
+import gleamy/red_black_tree_set
+
+pub fn production_info(info: types.ProductionInfo) {
+  json.object([
+    #("co2", json.float(info.co2)),
+    #("duration", json.int(info.duration)),
+    #("last_power", json.float(info.last_power)),
+    #("lifetime", json.float(info.lifetime)),
+    #("today", json.float(info.today)),
+  ])
+}
+
+pub fn momentary_power(power: types.MomentaryPower) {
+  case power {
+    module_power.NotConnected -> json.string("NC")
+    module_power.Watts(int) -> json.int(int)
+  }
+}
+
+pub fn module_power(power: types.ModulePower) {
+  json.object([
+    #("id", json.string(power.id)),
+    #(
+      "power",
+      json.object(
+        power.power
+        |> dict.to_list()
+        |> list.map(fn(item) {
+          let #(k, v) = item
+          #(birl.to_iso8601(k), momentary_power(v))
+        }),
+      ),
+    ),
+  ])
+}
+
+pub fn module_dataset(dataset: types.ModuleDataset) {
+  json.object([
+    #(
+      "times",
+      dataset.times
+        |> red_black_tree_set.foldr([], fn(acc, time) {
+          [birl.to_iso8601(time), ..acc]
+        })
+        |> json.array(json.string),
+    ),
+    #(
+      "datas",
+      json.object(
+        dataset.datas
+        |> dict.to_list()
+        |> list.map(fn(item) {
+          let #(k, v) = item
+          #(k, module_power(v))
+        }),
+      ),
+    ),
+  ])
+}
+
+pub fn dataset(dataset: types.Dataset) {
+  json.object([
+    #("production_info", production_info(dataset.production_info)),
+    #("modules", module_dataset(dataset.modules)),
+  ])
+}
diff --git a/backend/src/aurinko_backend.gleam b/backend/src/aurinko_backend.gleam
index bceb8d2..954e709 100644
--- a/backend/src/aurinko_backend.gleam
+++ b/backend/src/aurinko_backend.gleam
@@ -1,7 +1,6 @@
-import aurinko/pubsub as generic_pubsub
-import aurinko/registry
 import aurinko/updater
 import aurinko/updater/pubsub
+import aurinko/updater/registry
 import aurinko/web
 import dot_env
 import dot_env/env
@@ -26,7 +25,7 @@ pub fn main() {
       |> supervisor.add(
         supervisor.worker(fn(_) { pubsub.init() })
         |> supervisor.returning(fn(_, updater_pubsub_subject) {
-          generic_pubsub.from_subject(updater_pubsub_subject)
+          pubsub.from_subject(updater_pubsub_subject)
         }),
       )
       |> supervisor.add(