---
title: Configure the Linker for ASP.NET Core 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: 11/21/2019
no-loc: [Blazor]
uid: host-and-deploy/blazor/configure-linker
---
# Configure the Linker for ASP.NET Core Blazor

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

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

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

Control assembly linking using either of the following approaches:

* Disable linking globally with a [MSBuild property](#disable-linking-with-a-msbuild-property).
* Control linking on a per-assembly basis with a [configuration file](#control-linking-with-a-configuration-file).

## Disable linking with a MSBuild property

Linking is enabled by default 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

Control linking on a per-assembly basis by providing an XML configuration file and specifying the file as a MSBuild item in the project file:

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

*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>
```

For more information, see [IL Linker: Syntax of xml descriptor](https://github.com/mono/linker/blob/master/src/linker/README.md#syntax-of-xml-descriptor).

### Configure the linker for internationalization

By default, Blazor's linker configuration for Blazor WebAssembly apps strips out internationalization information except for locales explicitly requested. Removing these assemblies minimizes the app's size.

To control which I18N assemblies are retained, set the `<MonoLinkerI18NAssemblies>` MSBuild property in the project file:

```xml
<PropertyGroup>
  <MonoLinkerI18NAssemblies>{all|none|REGION1,REGION2,...}</MonoLinkerI18NAssemblies>
</PropertyGroup>
```

| Region Value     | Mono region assembly    |
| ---------------- | ----------------------- |
| `all`            | All assemblies included |
| `cjk`            | *I18N.CJK.dll*          |
| `mideast`        | *I18N.MidEast.dll*      |
| `none` (default) | None                    |
| `other`          | *I18N.Other.dll*        |
| `rare`           | *I18N.Rare.dll*         |
| `west`           | *I18N.West.dll*         |

Use a comma to separate multiple values (for example, `mideast,west`).

For more information, see [I18N: Pnetlib Internationalization Framework Libary (mono/mono GitHub repository)](https://github.com/mono/mono/tree/master/mcs/class/I18N).