Serilog

Serilog is a diagnostic logging library for the .NET platform that emphasizes structured logging. Unlike traditional simple text logs, Serilog records log events as structured data, enabling rich querying and analysis by downstream systems. A log event includes a message template and a set of properties, which can be serialized to JSON or other formats by sinks.

Developed by Nicholas Blumhardt, Serilog integrates with the .NET logging ecosystem and can be used as a drop-in replacement or as a provider for Microsoft.Extensions.Logging. It supports a pluggable sink architecture, allowing log events to be written to multiple destinations such as console output, files, databases, and centralized logging systems. Common sinks include Console, File, Seq (a structured log server), Elasticsearch, and various cloud logging services.

The ecosystem also includes enrichers, which add contextual properties like machine name, thread id, or user information to log events automatically, and the ability to destructure complex objects. Configuration is fluent and can be performed at application startup, with support for asynchronous logging, batching, and roll-up strategies.

Serilog supports standard log levels (Verbose, Debug, Information, Warning, Error, Fatal) and structured message templates, enabling filters and aggregations on properties rather than only on text. License and availability: Serilog is open source under the Apache 2.0 license and maintained by a community-driven ecosystem. It is widely used in .NET applications and integrates with modern .NET tooling and frameworks.