Logger Component

The logger component automatically logs all log messages through the serial port and through MQTT topics (if there is an MQTT client in the configuration). By default, all logs with a severity DEBUG or higher will be shown. Increasing the log level severity (to e.g INFO or WARNING) can help with the performance of the application and memory size.

# Example configuration entry
  level: DEBUG

Configuration variables:

  • baud_rate (Optional, int): The baud rate to use for the serial UART port. Defaults to 115200. Set to 0 to disable logging via UART.

  • level (Optional, string): The global log level. Any log message with a lower severity will not be shown. Defaults to DEBUG.

  • logs (Optional, mapping): Manually set the log level for a specific component or tag. See Manual Log Levels for more information.

  • id (Optional, ID): Manually specify the ID used for code generation.

Advanced settings:

  • tx_buffer_size (Optional, int): The size of the buffer used for log messages. Decrease this if you’re having memory problems. Defaults to 512.

  • hardware_uart (Optional, string): The Hardware UART to use for logging. Defaults to UART0.

  • esp8266_store_log_strings_in_flash (Optional, boolean): If set to false, disables storing log strings in the flash section of the device (uses more memory). Defaults to true.

  • on_message (Optional, Automation): An action to be performed when a message is to be logged. The variables int level, const char* tag and const char* message are available for lambda processing.

  • deassert_rts_dtr (Optional, boolean): Deasserts RTS/DTR when opening log over UART. This is useful if RTS/DTR signals are directly connected to the reset pin or strapping pins. Note: Deassert typically means high on TTL level since RTS/DTR are usually low active signals. Defaults to false.

Hardware UARTs

The logger component makes use of platform-specific hardware UARTs for serial logging. By default, the logger will occupy UART0. The ESP32 has three hardware UARTs, all of which can be used for both transmit and receive. The ESP8266 only has two hardware UARTs, one of which is transmit-only. The ESP8266 UART0 can also be ‘swapped’ to TX/RX on the CTS/RTS pins, if you need to use GPIO1 and GPIO3 for something else. Note that the common NodeMCU boards have their USB-UART Adapters fixed to the default GPIOs used by UART0, so if you use anything else you will not get log messages over the on-board USB.

Possible Hardware UART configurations:

  • UART0 - TX: GPIO1, RX: GPIO3

  • UART0_SWAP - TX: GPIO15, RX: GPIO13 (Only on ESP8266)

  • UART1 - TX: GPIO2, RX: None (Only on ESP8266)

  • UART1 - TX: GPIO9, RX: GPIO10 (Only on ESP32)

  • UART2 - TX: GPIO16, RX: GPIO17 (Only on ESP32 but not ESP32S2, ESP32S3 or ESP32C3)

  • USB_CDC - uses the USB CDC driver (Only on ESP32S2 and ESP32S3)

  • USB_SERIAL_JTAG - uses the USB Serial/JTAG driver (Only on ESP32S3 and ESP32C3)

Log Levels

Possible log levels are (sorted by severity):

  • NONE

  • No messages are logged.


  • With this log level, only errors are logged. Errors are issues that prevent the ESP from working correctly. Color: red

  • WARN

  • With this log level, warnings and errors are logged. Warnings are issues like invalid readings from sensors that ESPHome can recover from. Color: yellow

  • INFO

  • With this log level, everything up to info messages are logged; so errors, warnings and info. Color: green

  • DEBUG (Default)

  • Everything up to this log level is logged. Debug messages include the current readings from a sensor and status messages. Color: cyan


  • Like debug, but a few more messages that are usually deemed to be spam are also included. Color: grey


  • All internal messages are logged. Including all the data flowing through data buses like I²C, SPI or UART. Warning: May cause the device to slow down and have trouble staying connecting due to amount of generated messages. Color: white

Manual Tag-Specific Log Levels

If some component is spamming the logs and you want to manually set the log level for it, first identify the tag of the log messages in question and then disable them in your configuration.

Suppose we want to have verbose log messages globally, but the MQTT client spams too much. In the following example, we’d first see that the tag of the MQTT client is mqtt.client (before the first colon) and the tag for MQTT components is mqtt.component.


Next, we can manually set the log levels in the configuration like this:

  level: VERBOSE
    mqtt.component: DEBUG
    mqtt.client: ERROR

Please note that the global log level determines what log messages are saved in the binary. So for example an INFO global log message will purge all DEBUG log statements from the binary in order to conserve space. This however means that you cannot set tag-specific log levels that have a lower severity than the global log level.

logger.log Action

Print a formatted message to the logs.

In the format option, you can use printf-style formatting (see Formatted Text).

    - logger.log: "Hello World"

    # Formatted:
    - logger.log:
        format: "The temperature sensor reports value %.1f and humidity %.1f"
        args: [ 'id(temperature_sensor).state', 'id(humidity_sensor).state' ]

Configuration options:

  • format (Required, string): The format for the message in printf-style.

  • args (Optional, list of lambda): The optional arguments for the format message.

  • level (Optional, string): The log level to print the message with. Defaults to DEBUG.

  • tag (Optional, string): The tag (seen in front of the message in the logs) to print the message with. Defaults to main.

Logger Automation


This automation will be triggered when a new message is added to the log. In lambdas you can get the message, log level and tag from the trigger using message (const char *), level (int) and tag (const char *).

  # ...
    level: ERROR
      - mqtt.publish:
          topic: some/topic
          payload: !lambda |-
            return "Triggered on_message with level " + to_string(level) + ", tag " + tag + " and message " + message;


Logging will not work in the on_message trigger. You can’t use the logger.log action and the ESP_LOGx logging macros in this automation.

See Also