---
title: Write log messages
slug: cms-13/docs/write-log-messages
docTags: 
createdAt: 2026-07-30T20:22:10.689Z
---

Write log messages through the .NET Core `Microsoft.Extensions.Logging` API to keep CMS and custom application logs in a single, consistent output. Optimizely CMS 13 uses this API, so all logs flow to the same configured destination.

The `EPiServer.Logging` namespace provides a facade over `Microsoft.Extensions.Logging`. To manage logger configuration and output, go to [Logging in .NET Core](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/logging/?view=aspnetcore-5.0).

:::hint{type="info"}
**Backward compatibility**
Existing projects that use the `EPiServer.Logging` API continue to work because the API acts as a facade over `Microsoft.Extensions.Logging`. For new projects, log directly through the `Microsoft.Extensions.Logging` API.
:::