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Batteries included::
Log4j bundles a rich set of components to assist various use cases.
* xref:manual/appenders.adoc[Appenders] targeting files, network sockets, databases, SMTP servers, etc.
* xref:manual/layouts.adoc[Layouts] that can render CSV, HTML, JSON, Syslog, etc. formatted outputs
* xref:manual/filters.adoc[Filters] based on log event rates, regular expressions, scripts, time, etc.
* xref:manual/lookups.adoc[Lookups] for accessing system properties, environment variables, log event fields, etc.

Reliability::
Log4j is built with solid reliability in mind.
It can automatically reload its configuration upon modification and will do so without losing log events while reconfiguration occurs.

Performance::
When configured correctly, Log4j can deliver excelling performance without almost any burden on the Java garbage collector, and it will do so without sacrificing reliability.
Check out the xref:manual/performance.adoc[Performance] page for details.

Extensibility::
Log4j contains a fully-fledged xref:manual/plugins.adoc[plugin support] that users can leverage to extend functionality.
You can easily add your components (layouts, appenders, filters, etc.) or customize existing ones (e.g., adding new directives to xref:manual/pattern-layout.adoc#extending[Pattern Layout] or xref:manual/json-template-layout.adoc#extending[JSON Template Layout]).
Check out the xref:manual/extending.adoc[Extending Log4j] page.

Powerful API::
Log4j is a logging system where the API (called Log4j API) and its implementation (called Log4j Core) is distinctly separate from each other.
xref:manual/api.adoc[Log4j API] provides the most feature-rich logging facade in the market; support for various `Message` types (such as `Object` or `Map`) besides plain `String`, lambda expressions, parameterized logging, markers, levels, diagnostic contexts (aka. MDC/NDC), etc.
Log4j team takes backward compatibility very seriously and makes sure people relying on Log4j API gets a logging facade that is straightforward to use in a correct and future-proof way.
Check out the xref:manual/api.adoc[Java API],
{logging-services-url}/log4j/kotlin/index.html[Kotlin API]
and
{logging-services-url}/log4j/scala/index.html[Scala API]
pages for further information.

No vendor lock-in::
Log4j API is a generic logging facade for various logging frameworks.
While Log4j Core implements it at its fullest, you can easily switch to other implementations such as Logback or JUL (`java.util.logging`).
