---
title: Configure the Linker for Blazor
author: guardrex
description: Learn how to control the Intermediate Language (IL) Linker when building a Blazor app.
monikerRange: '>= aspnetcore-3.0'
ms.author: riande
ms.custom: mvc
ms.date: 01/29/2019
uid: host-and-deploy/razor-components/configure-linker
---
# Configure the Linker for Blazor

By [Luke Latham](https://github.com/guardrex)

[!INCLUDE[](~/includes/razor-components-preview-notice.md)]

Blazor performs [Intermediate Language (IL)](/dotnet/standard/managed-code#intermediate-language--execution) linking during each Release mode build to remove unnecessary IL from the output assemblies.

You can control assembly linking with either of the following approaches:

* Disable linking globally with an MSBuild property.
* Control linking on a per-assembly basis with a configuration file.

## Disable linking with an MSBuild property

Linking is enabled by default in Release mode when an app is built, which includes publishing. To disable linking for all assemblies, set the `<BlazorLinkOnBuild>` MSBuild property to `false` in the project file:

```xml
<PropertyGroup>
  <BlazorLinkOnBuild>false</BlazorLinkOnBuild>
</PropertyGroup>
```

## Control linking with a configuration file

Linking can be controlled on a per-assembly basis by providing an XML configuration file and specifying the file as an MSBuild item in the project file.

The following is an example configuration file (*Linker.xml*):

```xml
<?xml version="1.0" encoding="UTF-8" ?>
<!--
  This file specifies which parts of the BCL or Blazor packages must not be
  stripped by the IL Linker even if they aren't referenced by user code.
-->
<linker>
  <assembly fullname="mscorlib">
    <!--
      Preserve the methods in WasmRuntime because its methods are called by 
      JavaScript client-side code to implement timers.
      Fixes: https://github.com/aspnet/Blazor/issues/239
    -->
    <type fullname="System.Threading.WasmRuntime" />
  </assembly>
  <assembly fullname="System.Core">
    <!--
      System.Linq.Expressions* is required by Json.NET and any 
      expression.Compile caller. The assembly isn't stripped.
    -->
    <type fullname="System.Linq.Expressions*" />
  </assembly>
  <!--
    In this example, the app's entry point assembly is listed. The assembly
    isn't stripped by the IL Linker.
  -->
  <assembly fullname="MyCoolBlazorApp" />
</linker>
```

To learn more about the file format for the configuration file, see [IL Linker: Syntax of xml descriptor](https://github.com/mono/linker/blob/master/linker/README.md#syntax-of-xml-descriptor).

Specify the configuration file in the project file with the `BlazorLinkerDescriptor` item:

```xml
<ItemGroup>
  <BlazorLinkerDescriptor Include="Linker.xml" />
</ItemGroup>
```