Web Server API
==============

.. seo::
    :description: Migration guide for installing ESPHome on ESPs running ESPEasy.
    :image: espeasy.png

Since version 1.3, ESPHome includes a built-in web server that can be used to view states
and send commands. In addition to visible the web-frontend available under the root index of the
web server, there's also two other features the web server currently offers: A real time event
source and REST API.

Note that the web server is only and will only ever be intended to view and edit states. Specifically
not something like configuring the node, as that would quickly blow up the required flash and
memory size.

First up, to use the web server enable it using ``App.init_web_server()`` directly from code
or using the :doc:`Web Server Section </components/web_server>` in ESPHome.
Then, navigate to the front end interface with the IP of the node or alternatively using
mDNS with ``<name>.local/``. So for example to navigate to the web server of a node called
``livingroom``, you would enter ``livingroom.local/`` in your browser.

While it's currently recommended to use ESPHome directly through Home Assistant, if you want
to integrate ESPHome with an external or self-built application you can use two available
APIs: the real-time event source API and REST API.

Event Source API
~~~~~~~~~~~~~~~~

If you want to receive real-time updates for sensor state updates, it's recommended to use
the Event Source Web API. With the URL ``/events``, you can create an
`Event Source <https://developer.mozilla.org/en-US/docs/Web/API/EventSource>`__ that receives
real-time updates of states and the debug log using server-sent events.
Event sources are easy to implement in many languages and already have many libraries
available. For example `eventsource for node.js <https://github.com/EventSource/eventsource>`__
and `eventsource for python <https://pypi.org/project/eventsource/1.1.1/>`__.

Currently, there are three types of events sent: ``ping``, ``state`` and ``log``. The first one
is repeatedly sent out to keep the connection alive. ``log`` events are sent every time a log
message is triggered and is used to show the debug log on the index page.  ``state`` is where
the real magic happens. All events with this type have a JSON payload that describes the state
of a component. Each of these JSON payloads have two mandatory fields: ``id`` and ``state``. ID
is the unique identifier of the component and is prefixed with the domain of the component, for
example ``sensor``. ``state`` contains a simple text-based representation of the state of the
underlying component, for example ON/OFF or 21.4 °C. Several components also have additional
fields in this payload, for example lights have a ``brightness`` attribute.

.. figure:: /web-api/event-source.png
    :align: center

    Example payload of the event source API.

Additionally, each time a client connects to the event source the server sends out all current
states so that the client can catch up with reality.

The payloads of these state events are also the same as the payloads of the REST API GET calls.
I would recommend just opening the network debug panel of your web browser to see what's sent.

REST API
--------

There's also a simple REST API available which can be used to get and set the current state. All
calls to this API follow the URL schema ``/<domain>/<id>[/<method>?<param>=<value>]``.
The ``domain`` is the type of the component, for example ``sensor`` or ``light``. ``id`` refers
to the id of the component - this ID is created by taking the name of the component, stripping out
all non-alphanumeric characters, making everything lowercase and replacing all spaces by underscores.

By creating a simple GET request for a URL of the form ``/<domain>/<id>`` you will get a JSON payload
describing the current state of the component. This payload is equivalent to the ones sent by the
event source API.

To actually *control* the state of a component you need to send a POST request with a ``method`` like
``turn_on``. For example, to turn on a light, you would send a POST request to
``/light/livingroom_lights/turn_on``. Some components also optionally accept URL parameters to control
some other aspects of a component, for example the brightness of a light.

Sensor
******

Sensors only support GET requests by sending a request to ``/sensor/<id>``. For example sending
a GET request to ``/sensor/outside_temperature`` could yield this payload:

.. code-block:: json

    {
      "id": "sensor-outside_temperature",
      "state": "19.8 °C",
      "value": 19.76666
    }


-  **id**: The id of the sensor. Prefixed by ``sensor-``.
-  **state**: The text-based state of the sensor as a string.
-  **value**: The floating point (filtered) value of the sensor.

Binary Sensor
*************

Binary sensors have a similar payload and also only support GET requests. For example requesting
the current state of a binary sensor using the URL ``binary_sensor/living_room_status`` could
result in following payload:

.. code-block:: json

    {
      "id": "binary_sensor-living_room_status",
      "state": "ON",
      "value": true
    }


-  **id**: The id of the binary sensor. Prefixed by ``binary_sensor-``.
-  **state**: The text-based state of the binary sensor as a string.
-  **value**: The binary (``true``/``false``) state of the binary sensor.

Switch
******

Switches have the exact same properties as a binary sensor in the state reporting aspect, but they
additionally support setting states with the ``turn_on``, ``turn_off`` and ``toggle`` methods.

Each of these is quite self explanatory. Creating a POST request to ``/switch/dehumidifier/turn_on``
would for example result in the component called "Dehumidifier" to be turned on. The server will respond
with a 200 OK HTTP return code if the call succeeded.

Light
*****

Lights support quite a few more complicated options, like brightness or color. But first, to get
the state of a light, send a GET request to ``/light/<id>``, for example ``light/living_room_lights``.

.. code-block:: json

    {
      "id": "light-living_room_lights",
      "state": "ON",
      "brightness": 255,
      "color": {
        "r": 255,
        "g": 255,
        "b": 255
      },
      "effect": "None",
      "white_value": 255
    }


-  **id**: The id of the light. Prefixed by ``light-``.
-  **state**: The text-based state of the light as a string.
-  **brightness**: The brightness of the light from 0 to 255. Only if the light supports brightness.
   If ``state`` is ``OFF``, this can still report values like 255 in order to send the full state.
-  **color**: The color of this light, only if it supports color.

   -  **r**: The red channel of this light. From 0 to 255.
   -  **g**: The green channel of this light. From 0 to 255.
   -  **b**: The blue channel of this light. From 0 to 255.

-  **effect**: The currently active effect, only if the light supports effects.
-  **white_value**: The white value of RGBW lights. From 0 to 255.

Setting light state can happen through three POST method calls: ``turn_on``, ``turn_off`` and ``toggle``.
Turn on and off have additional URL encoded parameters that can be used to set other properties. For example
creating a POST request at ``/light/<id>/turn_on?brightness=128&transition=2`` will create transition with length
2s to the brightness 128 while retaining the color of the light.

``turn_on`` optional URL parameters:

-  **brightness**: The brightness of the light, from 0 to 255.
-  **r**: The red color channel of the light, from 0 to 255.
-  **g**: The green color channel of the light, from 0 to 255.
-  **b**: The blue color channel of the light, from 0 to 255.
-  **white_value**: The white channel of RGBW lights, from 0 to 255.
-  **flash**: Flash the color provided by the other properties for a duration in seconds.
-  **transition**: Transition to the specified color values in this duration in seconds.
-  **effect**: Set an effect for the light.

``turn_off`` optional URL parameters:

-  **transition**: Transition to off in this duration in seconds.

Fan
***

Fans are similar to switches as they can be turned on/off and toggled. In addition, if the
underlying fan supports it, fans in the web server also support the speed settings "low",
"medium" and "high" and an oscillation setting. To get the current state of a fan, create a
GET request to ``/fan/<id>``.

.. code-block:: json

    {
      "id": "fan-living_room_fan",
      "state": "ON",
      "value": true,
      "speed": "high",
      "oscillation": false
    }


-  **id**: The id of the fan. Prefixed by ``fan-``.
-  **state**: The text-based state of the fan as a string.
-  **value**: The binary (``true``/``false``) state of the fan.
-  **speed**: The speed setting of the fan if it's supported. Either "off", "low", "medium" or "high".
-  **oscillation**: Whether the oscillation setting of the fan is on. Only sent if the fan supports it.

To control the state of the fan, send POST requests to ``/fan/<id>/turn_on``, ``/fan/<id>/turn_off``
and ``/fan/<id>/toggle``. Turn on additionally supports these optional parameters:

-  **speed**: The new speed setting of the fan. Values as above.
-  **oscillation**: The new oscillation setting of the fan. Values as above.
