What is the 'Fatal' level in logging?

Fatal — this is the highest level of severity in logging, used to record events that lead to immediate and irreversible termination of the application. A Fatal level error indicates a state from which recovery is impossible without a restart or external intervention. Such an event requires immediate attention from the development or support team.

Examples of usage:

• Inability to connect to a critical resource (e.g., database) at application startup.
• An unexpected exception that completely stops the program execution without the possibility of proper termination.
• Data integrity violation detected during execution that makes further work pointless.

Fatal level logs are usually sent to a centralized monitoring and alerting system so that responsible persons can quickly respond to the problem.

Depending on the logging library or framework used, this level may be called differently (e.g., Critical), but the essence remains the same – recording critical, unrecoverable failures.