dotnet/AspNetCore.Docs · error · Error

response.statusText

Error message

response.statusText

What it means

JavaScript Error thrown inside loadBootResource when the Brotli-compressed (.br) resource fetch fails (response.ok is false). The custom boot-resource loader fetches defaultUri + '.br' with cache:'no-cache' for non-localhost, non-js/config/manifest resources and throws response.statusText if the fetch returns a non-OK HTTP status. Applies to ASP.NET Core 8.0+ (the >= aspnetcore-8.0 moniker).

Source

Thrown at aspnetcore/blazor/host-and-deploy/webassembly/index.md:146

:::moniker range=">= aspnetcore-8.0 < aspnetcore-11.0"

Blazor Web App:

:::moniker-end

:::moniker range=">= aspnetcore-8.0"

```html
<script type="module">
  import { BrotliDecode } from './decode.min.js';
  Blazor.start({
    webAssembly: {
      loadBootResource: function (type, name, defaultUri, integrity) {
        if (type !== 'dotnetjs' && location.hostname !== 'localhost' && type !== 'configuration' && type !== 'manifest') {
          return (async function () {
            const response = await fetch(defaultUri + '.br', { cache: 'no-cache' });
            if (!response.ok) {
              throw new Error(response.statusText);
            }
            const originalResponseBuffer = await response.arrayBuffer();
            const originalResponseArray = new Int8Array(originalResponseBuffer);
            const decompressedResponseArray = BrotliDecode(originalResponseArray);
            const contentType = type === 
              'dotnetwasm' ? 'application/wasm' : 'application/octet-stream';
            return new Response(decompressedResponseArray, 
              { headers: { 'content-type': contentType } });
          })();
        }
      }
    }
  });
</script>
```

:::moniker-end

View on GitHub (pinned to c67a80103a)

Solutions

1. Verify the published wwwroot/_framework contains .br files for each boot resource.
2. Configure the static-file middleware / web server to serve precompressed Brotli assets with correct Content-Encoding.
3. If hosting without precompression, remove or simplify loadBootResource so it does not append '.br'.
4. Check the failing resource's URL and statusText in the browser devtools Network tab to identify 404/403/etc.
5. Ensure the CDN/proxy serves the same files for the .br suffix and does not require auth.

Example fix

// before
const response = await fetch(defaultUri + '.br', { cache: 'no-cache' });
if (!response.ok) {
  throw new Error(response.statusText);
}

// after — fall back to uncompressed on failure
let response = await fetch(defaultUri + '.br', { cache: 'no-cache' });
if (!response.ok) {
  console.warn(`Brotli fetch failed (${response.status}) for ${defaultUri}; falling back.`);
  response = await fetch(defaultUri, { cache: 'no-cache' });
  if (!response.ok) {
    throw new Error(`Boot resource ${defaultUri} failed: ${response.statusText}`);
  }
  return response;
}

// Validate .br availability before relying on it
const probe = await fetch(defaultUri + '.br', { method: 'HEAD' });
if (!probe.ok) { /* skip compression path */ }

function canServeBrotli() {
  return 'DecompressionStream' in window || typeof BrotliDecode === 'function';
}

try {
  const response = await fetch(defaultUri + '.br', { cache: 'no-cache' });
  if (!response.ok) throw new Error(response.statusText);
  // decompress...
} catch (err) {
  console.warn('Brotli load failed, falling back:', err);
  return fetch(defaultUri, { cache: 'no-cache' });
}

When it happens

Trigger: Hosting environment does not serve .br files (compression not enabled or files not published), CDN returns a 404/403 for the .br variant, MIME type misconfiguration causing 404, deployment missing the compressed assets, or a network/CDN transient error returning non-2xx.

Common situations: Publishing without Brotli compression enabled; reverse proxy stripping or not serving precompressed files; CDN cache miss for the .br variant; deployment that omitted wwwroot/_framework compressed files; CORS/auth on the static file endpoint returning 401/403.

Related errors

• ko.mapping.updateFromJS, use ko.mapping.fromJS instead. Plea
• ko.mapping.updateFromJSON, use ko.mapping.fromJSON instead.
• Must provide a non-empty value for the "src" attribute.

AI-assisted analysis of dotnet/AspNetCore.Docs@c67a80103a (2026-08-13). Data as JSON: /api/errors/eba34f0599db6e9b. Report an issue: GitHub.