kb(deployment): failed to compile, expected magic word

Author: marin-bratanov

knowledge-base/images/wasm-fail-to-compile-magic-word.png

@@ -0,0 +1,51 @@
+---
+title: Failed to execute compile on WebAssembly - expected magic word 00 61 73 6d
+description: WASM Compile Error When Hosted - expected magic word and fail to execute compile
+type: troubleshooting
+page_title: WASM Compile Error When Hosted - expected magic word 00 61 73 6d
+slug: common-kb-wasm-magic-word
+position: 
+tags: 
+ticketid: 1451701
+res_type: kb
+---
+
+## Environment
+<table>
+	<tbody>
+	    <tr>
+			<td>Hosting</td>
+			<td>cloudflare.com integration with smarterasp.net, may affect others</td>
+		</tr>
+		<tr>
+			<td>Environment</td>
+			<td>WASM Blazor app</td>
+		</tr>
+	</tbody>
+</table>
+
+
+## Description
+Publishing a client-side (WASM) Blazor app may fail with messages similar to the error below.
+
+A particular environment is an ASP.NET Core hosted Blazor project hosted on smarterAsp.net with the automatic config which enabled caching and compacting with cloudflare.com.
+
+
+
+## Error Message
+* WASM: wasm streaming compile failed: Failed to execute 'compile' on 'WebAssembly': Incorrect response MIME type. Expected 'application/wasm'
+* WASM: failed to asynchronously prepare wasm: CompileError: WebAssembly.instantiate(): expected magic word 00 61 73 6d, found ef bb bf 3c @+0
+* CompileError: WebAssembly.instantiate(): expected magic word 00 61 73 6d, found ef bb bf 3c @+0
+
+![failed to compile expected magic word](images/wasm-fail-to-compile-magic-word.png)
+
+## Cause\Possible Cause(s)
+The errors indicate the following issues:
+
+* The MIME type for the `wasm` files is wrong - it must be `application/wasm` but the hosting environment used the wrong one
+* The wasm file is broken (for example, archived, compressed twice or otherwise truncated/modified).
+
+## Solution
+The general solution is to make sure that the application files are not tampered with and that you have the correct server settings as per Microsoft's documentation: [https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/blazor/webassembly?view=aspnetcore-3.1](https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/blazor/webassembly?view=aspnetcore-3.1)
+
+In the particular smarterasp.net hosting case, disabling the cloudflare integration resolved the issue.