Overview

Startup is asynchronous and automatic via blazor.web|server|webassembly.js.

manually starting blazor

manually starting blazor web app

Add autostart="false" to the Blazor <script> tag.
Place a script that calls Blazor.start() after the <script> tag inside the closing <body> tag.
Place static SSR options in the ssr property.
Place server-side Blazor SignalR circuit options in the circuit property.
Place client-side WebAssembly options in the webAssembly property.

<script src="{BLAZOR SCRIPT}" autostart="false"></script>
<script>
  ...
  Blazor.start({
    ssr: {
      ...
    },
    circuit: {
      ...
    },
    webAssembly: {
      ...
    }
  });
  ...
</script>

manually starting standalone blazor wasm and blazor server

Add autostart="false" to the Blazor <script> tag.
Place a script that calls Blazor.start() after the <script> tag inside the closing <body> tag.
Add any options in the Blazor.start() parameter.

<script src="{BLAZOR SCRIPT}" autostart="false"></script>
<script>
  ...
  Blazor.start({
    ...
  });
  ...
</script>

javascript initializers

JS initializers execute logic before and after a Blazor app loads.

More: https://learn.microsoft.com/en-us/aspnet/core/blazor/fundamentals/startup?view=aspnetcore-9.0#javascript-initializers

initialize blazor when the document is ready

<script src="{BLAZOR SCRIPT}" autostart="false"></script>
<script>
  document.addEventListener("DOMContentLoaded", function() {
    Blazor.start();
  });
</script>