The logging configuration file logging.yaml for OctoPrint is expected in its settings folder, which unless defined differently on the command line is located at ~/.octoprint on Linux, at %APPDATA%/OctoPrint on Windows and at ~/Library/Application Support/OctoPrint on macOS.

You can use it to change the log levels of the individual components within OctoPrint, which might be necessary to help in debugging issues you are experiencing, or to change the configuration of the logging handlers themselves, e.g. in order to change size after which to rollover the serial.log.

Changing log levels

If you need to change the default logging level within OctoPrint, create the file with a text editor of your choice (it’s usually not there). The general format is this:

    level: <loglevel>

with <component> being the internal OctoPrint component for which to change the loglevel, and <loglevel> being the new log level to set. An example for increasing the log level of the events and the file management components to DEBUG (the highest amount of logging) would be this logging.yaml:

    level: DEBUG
    level: DEBUG

A list of important components for which an increase in logging might be interesting follows:

  • octoprint.events: the event sub system

  • octoprint.filemanager: the file management layer

  • octoprint.plugin: the plugin sub system

  • octoprint.plugins.<plugin>: the plugin <plugin>, e.g. octoprint.plugins.discovery to change the log level of the Discovery plugin or octoprint.plugins.backup to change the log level of the Backup plugin.

  • octoprint.slicing: the slicing sub system

This list will be expanded when deemed necessary.

Changing logging handlers

You can also change the configuration of the logging handlers themselves, e.g. in order to make the serial.log larger for debugging long running communications or to change the behaviour of the octoprint.log.

You can find the default configurations of the file handler used for the octoprint.log, the serialFile handler used for the serial.log and the console handler used for the output to stdout in YAML format below:

  # stdout
    class: logging.StreamHandler
    level: DEBUG
    formatter: colored
    stream: ext://sys.stdout

  # octoprint.log
    class: logging.handlers.TimedRotatingFileHandler
    level: DEBUG
    formatter: simple
    when: D
    backupCount: 1
    filename: /path/to/octoprints/logs/octoprint.log

  # serial.log
    class: logging.handlers.RotatingFileHandler
    level: DEBUG
    formatter: simple
    maxBytes: 2097152 # 2 * 1024 * 1024 = 2 MB in bytes
    filename: /path/to/octoprints/logs/serial.log


If OctoPrint is instructed to not color its logging output (e.g. via the --no-color command line option or the NO_COLOR environment variable), the colored formatter will be replaced with the simple formatter.

You can find more information on the used logging handlers in the Python documentation on logging.handlers.

Changing logging formatters

The logging formatters can be defined via logging.yaml as well. The simple formatter as referenced above is expressed in YAML as follows:

    format: "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
    format: "%(log_color)s%(asctime)s - %(name)s - %(levelname)s - %(message)s%(reset)s"

As example, if you want to change the format to include the full file and line number in which the logging statement was issued, you could redefine the formatters as follows:

  format: "%(asctime)s - %(name)s - %(pathname)s%(filename)s#%(lineno)d - %(levelname)s - %(message)s"
  format: "%(log_color)s%(asctime)s - %(name)s - %(pathname)s%(filename)s#%(lineno)d - %(levelname)s - %(message)s%(reset)s"

The possible keys for the logging format can be found in the Python documentation on LogRecord attributes.