The web_server component creates a simple web server on the node that can be accessed through any browser and a simple REST API. Please note that enabling this component will take up a lot of memory and can lead to problems, especially on the ESP8266.
To navigate to the web server in your browser, either use the IP address of the node or use <node_name>.local/ (note the trailing forward slash) via mDNS.
To conserve flash size, the CSS and JS files used on the root page to show a simple user interface are hosted by esphome.io. If you want to use your own service, use the css_url and js_url options in your configuration.
port (Optional, int): The port the web server should open its socket on.
css_url (Optional, url): The URL that should be used for the CSS stylesheet. Defaults to https://esphome.io/_static/webserver-v1.min.css (updates will go to v2, v3, etc).
js_url (Optional, url): The URL that should be used for the JS script. Defaults to https://esphome.io/_static/webserver-v1.min.js.
Starting with version 1.9.0, you can also upload firmware files OTA with the web server.