Blazor WebAssembly Standalone template incorrectly fingerprints _framework runtime files when OverrideHtmlAssetPlaceholders=true (VS 2026 / .NET 10)

[suntaurus]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When creating a Blazor WebAssembly Standalone App in Visual Studio 2026 (latest release), the generated .csproj includes:

<OverrideHtmlAssetPlaceholders>true</OverrideHtmlAssetPlaceholders>

With this enabled, the publishing pipeline incorrectly fingerprints _framework runtime files, such as:

_framework/blazor.webassembly.js → blazor.webassembly..js

However, the template’s index.html still references:

<script src="_framework/blazor.webassembly.js"></script>

Since the file has been renamed but the HTML is not updated, the app fails to load after deployment (especially to static hosts like Azure Static Web Apps).

This behavior breaks all newly created Blazor WebAssembly Standalone apps in .NET 10 / VS 2026.

Even if we try to enable fingerprinting in the index.html like below

<script src="_framework/blazor.webassembly#[.{fingerprint}].js"></script>

Then when we run we get error

blazor.webassembly.66stpp682q.js:1 Uncaught (in promise) Error: Failed to start platform. Reason: TypeError: Failed to fetch dynamically imported module: https://xxxxxxx-preview.westeurope.1.azurestaticapps.net/_framework/dotnet.js at qt (blazor.webassembly.66stpp682q.js:1:58420)

If we set OverrideHtmlAssetPlaceholders = false or remove the attribute completely from the .csproj, then all works fine

Expected Behavior

No response

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

No response

Anything else?

No response

[javiercn]

@suntaurus thanks for contacting us.

Are you talking about this during development/build time or after you have published?

[suntaurus]

@suntaurus thanks for contacting us.

Are you talking about this during development/build time or after you have published?

locally it works, but when published it fails

[suntaurus]

it works fine during development, but when published it fails

[javiercn]

@suntaurus thanks for the additional details.

Do you have the same issue if you publish from the command line?

[dotnet-policy-service]

Hi @@suntaurus. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[suntaurus]

I figured out the issue, <script type="importmap"> was missing in my index.html as a results it was not able to map the fingerprinted issue.

This happened when I upgraded my existing .net9 project to .net10 and tried to use fingerprinting for /blazor.webassembly.js but missed to add <script type="importmap"> to the header

[xdiegors]

I figured out the issue, <script type="importmap"> was missing in my index.html as a results it was not able to map the fingerprinted issue.

This happened when I upgraded my existing .net9 project to .net10 and tried to use fingerprinting for /blazor.webassembly.js but missed to add <script type="importmap"> to the header

This really helped me! Thanks!!!