Choose a .NET logging setup: ILogger, Serilog, NLog, or log4net

ILogger, Serilog, NLog, and log4net sit at different levels of a .NET logging setup. ILogger is an abstraction, while providers and frameworks handle formatting and delivery. Compare the combination your application will actually run, including its formatter, sinks, configuration, and runtime support.

Key points

• Microsoft.Extensions.Logging supplies the abstraction and several built-in providers. JSON console output is a valid structured logging option.
• Serilog is useful when message templates, destructuring, enrichment, and its sink integrations fit the application.
• NLog offers configurable targets and routing, including XML-based rules and reload support.
• log4net continues to receive releases. Its event-property model differs from Serilog's message-template API, but it can produce structured output through layouts and extensions.

Compare the components

Avoid selecting a stack from a star rating or an unverified performance ranking. The required destinations, runtime, schema, and operating model are more useful criteria.

1. Microsoft.Extensions.Logging

The abstraction supports categories, levels, message templates, scopes, and pluggable providers. ASP.NET Core integrates it with hosting and dependency injection. A simple service can use the built-in JSON console formatter and let its platform collect stdout.

Keeping business code on ILogger makes backend changes easier, but a migration still needs validation of filtering, scopes, exceptions, and output fields. Changing startup registration alone does not guarantee identical behavior.

2. Serilog

Serilog records named template properties such as {UserId} and can destructure an object with {@Order}. Sinks control delivery and formatters control serialized output. LogContext adds scoped properties when the logger is configured to enrich from it.

ASP.NET Core integration packages support host registration, including APIs such as AddSerilog or UseSerilog depending on the chosen integration and version. Choose packages compatible with the application's runtime and inspect each sink's buffering and failure behavior.

3. NLog

NLog separates targets from rules. Rules can route by logger and severity, select layouts per target, and suppress unwanted events. XML configuration with autoReload is useful when that deployment model permits configuration changes; it is not a promise that every external setting reloads automatically.

JsonLayout can preserve event properties for downstream analysis. Choose between NLog and Serilog based on needed routing, event APIs, integrations, and team familiarity, then test the same representative workload.

4. log4net

log4net remains a maintained Apache project, including 2026 releases. Its familiar logger/appender/layout model can be a good fit for an existing system. Event properties and structured XML layouts are available; JSON is commonly provided through an external layout extension. Its normal logging API does not have Serilog's same named-template and destructuring semantics.

Retaining a working log4net installation can be reasonable. For a new application, evaluate required features and extension maintenance rather than rejecting it solely on an outdated claim that it is inactive.

The application interface and the output are separate choices

Keeping call sites on ILogger can make provider changes easier. The output requirement then narrows the implementation: built-in JSON console logging may be enough for a small service, Serilog adds its template/enrichment/sink model, and NLog offers target routing and configuration rules. A working log4net application does not need migration solely to follow a new-project preference. The benefit has to outweigh changes in filters, fields, dependencies, and delivery behavior.

Verify collection after choosing a framework

Inspect a real event for timestamp, severity, exception, and request identifiers. Different formatters and layouts produce different JSON shapes. Update parsing rules as part of a logging-library migration.

For Guance, choose the appropriate file or container source using DataKit logging. Use Pipeline to map source fields to the expected event time and status. For trace-to-log navigation, emit a matching trace_id and verify service identity against the log correlation instructions.

Frequently asked questions

Does ILogger replace Serilog or NLog?

It can be used with them as providers. It can also be paired with built-in providers when those are sufficient. These are combinations of abstraction and implementation, not necessarily mutually exclusive alternatives.

How much faster is one framework?

There is no workload-independent answer. Compare enabled and disabled calls, serialization, synchronous versus asynchronous output, queue saturation, and destination latency. Both Serilog and NLog have asynchronous options, with different policies that need testing.

Can two frameworks coexist?

Yes, for example during migration. Make ownership and destinations explicit and check for duplicate events, conflicting filters, and inconsistent schemas. An eventual single backend may simplify operations, but coexistence is not inherently invalid.

What about .NET Framework applications?

Check the exact package version's target frameworks and those of every integration or sink. Historical support for .NET Framework 4.6.1 does not mean all current Serilog packages support it. Apply the same check to NLog and log4net. Validate encoding, multiline exceptions, and rotated paths before centralizing older applications.

Related reading

• log4net
• Java logging best practices
• Serilog
• NLog
• Choose a logging framework (Chinese)

References: Microsoft logging, Serilog, NLog, log4net releases, and log4net layouts.