---
title: Logging
slug: cms-12/docs/8-qD-logging
docTags: 
createdAt: 2026-08-10T15:55:56.000Z
---

:::hint{type="info"}
**Note**
To investigate and resolve issues, you should turn on logging for your application.
:::

The Logging API shipped with Optimizely Content Management System (CMS) is an abstraction for writing log messages from the system. It is used internally by the CMS assemblies for logging. When creating CMS sites using the Visual Studio integration, it installs the `EPiServer.Logging.Log4Net` package by default, which is the log4net implementation of the API. Optimizely Search & Navigation also uses the log4net framework.

To activate logging, add an appender and a logger in the `EPiServerLog.config`, located by default in the web root of your CMS or Optimizely Customized Commerce application, for the `EPiServer.Find` namespace.

```xml
<appender name="FindRollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
   <file value="find.log" />
   <appendToFile value="true" />
   <datePattern value=".yyyyMMdd.'log'" />
   <rollingStyle value="Date" />
   <filter type="log4net.Filter.LevelRangeFilter">
      <acceptOnMatch value="true" />
      <levelMin value="INFO" />
      <levelMax value="FATAL" />
   </filter>
   <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %level [%thread] %type.%method - %message%n" />
   </layout>
</appender>
<logger name="EPiServer.Find">
   <appender-ref ref="FindRollingLogFileAppender" />
</logger>
```

If your application does not have an `EPiServerLog.config`, create one in your application's web root folder and add the logger and appender there.

```xml
<?xml version="1.0" encoding="utf-8"?>
<log4net>
<appender name="FindRollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
   <file value="find.log" />
   <appendToFile value="true" />
   <datePattern value=".yyyyMMdd.'log'" />
   <rollingStyle value="Date" />
   <filter type="log4net.Filter.LevelRangeFilter">
      <acceptOnMatch value="true" />
      <levelMin value="INFO" />
      <levelMax value="FATAL" />
   </filter>
   <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %level [%thread] %type.%method - %message%n" />
   </layout>
</appender>
<logger name="EPiServer.Find">
   <appender-ref ref="FindRollingLogFileAppender" />
</logger>
</log4net>
```

See also [Write log messages](docId\:Ni_XRK-pGS7dSsnD0FYEE).