dotnet/runtime · error · Error

URLSearchParams is supported

Error message

URLSearchParams is supported

What it means

Thrown by withApplicationArgumentsFromQuery() when globalThis.URLSearchParams is undefined. The message text is misleading ('URLSearchParams is supported') — the intent is the opposite: URLSearchParams is NOT supported in this environment. Treat it as a feature-detection failure. URLSearchParams is available in all modern browsers and Node 10+, so this fires only in very old runtimes or stripped shells.

Solutions

1. Add a URLSearchParams polyfill (core-js or url-search-params-polyfill) before bootstrapping.
2. Upgrade the host runtime to a version with native URLSearchParams.
3. Skip withApplicationArgumentsFromQuery and pass args via withApplicationArguments.
4. If you control the host, register globalThis.URLSearchParams from your runtime.

Example fix

// before
builder.withApplicationArgumentsFromQuery(); // throws on old WebView

// after
import 'url-search-params-polyfill';
builder.withApplicationArgumentsFromQuery();

function hasURLSearchParams(): boolean {
  return typeof (globalThis as any).URLSearchParams === 'function';
}

function supportsUrlSearchParams(): boolean {
  return typeof (globalThis as any).URLSearchParams === 'function';
}

try { builder.withApplicationArgumentsFromQuery(); } catch (e) {
  if (/URLSearchParams/.test((e as Error).message)) {
    // polyfill or pass args explicitly
    builder.withApplicationArguments(/* args */);
  } else throw e;
}

When it happens

Trigger: Running in an ancient embedded JS engine (old WebView, legacy Edge, IE11 polyfill missing). A shell/host that intentionally removed URLSearchParams. Node older than 10 (unsupported). Some smart-TV/legacy mobile webviews.

Common situations: Polyfilled environment where the URLSearchParams polyfill was not loaded. Old WebView on Android <5. Custom JS host (V8 isolate) without the URL API.

Related errors

• This browser doesn't support fetch API. Please use a modern…
• This browser doesn't support fetch API. Please use a modern…
• Missing window to the query parameters from
• Missing window to the query parameters from
• No fetch implementation available

AI-assisted analysis of dotnet/runtime@60108ba66e (2026-08-10). Data as JSON: /api/errors/fda1b493d7abdbea. Report an issue: GitHub.

Appendix: source

Thrown at src/native/libs/Common/JavaScript/loader/host-builder.ts:75

    withDebugging(level: number): DotnetHostBuilder {
        mergeLoaderConfig({
            debugLevel: level
        });
        return this;
    }
    withMainAssembly(mainAssemblyName: string): DotnetHostBuilder {
        mergeLoaderConfig({
            mainAssemblyName: mainAssemblyName
        });
        return this;
    }
    withApplicationArgumentsFromQuery(): DotnetHostBuilder {
        if (!globalThis.window) {
            throw new Error("Missing window to the query parameters from");
        }

        if (typeof globalThis.URLSearchParams === "undefined") {
            throw new Error("URLSearchParams is supported");
        }

        const params = new URLSearchParams(globalThis.window.location.search);
        const values = params.getAll("arg");
        return this.withApplicationArguments(...values);
    }
    withApplicationEnvironment(applicationEnvironment?: string): DotnetHostBuilder {
        mergeLoaderConfig({
            applicationEnvironment: applicationEnvironment
        });
        return this;
    }
    withApplicationCulture(applicationCulture?: string): DotnetHostBuilder {
        mergeLoaderConfig({
            applicationCulture: applicationCulture
        });
        return this;
    }

View on GitHub (pinned to 60108ba66e)