parcel-bundler/parcel · error · Error

No dynamic require possible: ${module}

Error message

No dynamic require possible: ${module}

What it means

Thrown by Child.childInit when process.browser is true and the requested module is not '@parcel/core/src/worker.js'. In a browser bundle dynamic require() is impossible, so only the pre-bundled coreWorker reference is permitted; any other module name is rejected.

Source

Thrown at packages/core/workers/src/child.js:109

  messageListener(message: WorkerMessage): Async<void> {
    if (message.type === 'response') {
      return this.handleResponse(message);
    } else if (message.type === 'request') {
      return this.handleRequest(message);
    }
  }

  send(data: WorkerMessage): void {
    this.child.send(data);
  }

  async childInit(module: string, childId: number): Promise<void> {
    // $FlowFixMe
    if (process.browser) {
      if (module === '@parcel/core/src/worker.js') {
        this.module = coreWorker;
      } else {
        throw new Error('No dynamic require possible: ' + module);
      }
    } else {
      // $FlowFixMe this must be dynamic
      this.module = require(module);
    }
    this.childId = childId;

    if (this.module.childInit != null) {
      await this.module.childInit();
    }
  }

  async handleRequest(data: WorkerRequest): Promise<void> {
    let {idx, method, args, handle: handleId} = data;
    let child = nullthrows(data.child);

    const responseFromContent = (content: any): WorkerDataResponse => ({
      idx,

View on GitHub (pinned to 59484858a1)

Solutions

1. In browser builds, only request '@parcel/core/src/worker.js' as the child module.
2. Bundle any required plugin worker under that module id, or move the work to a handle-based call.
3. Run Parcel in Node where require(module) works for arbitrary modules.

Example fix

// before (browser)
child.childInit('./myPluginWorker.js', 0);

// after
child.childInit('@parcel/core/src/worker.js', 0);

if (process.browser && module !== '@parcel/core/src/worker.js') {
  throw new Error(`Browser child init requires the core worker module, got ${module}`);
}

When it happens

Trigger: Initializing a worker child in a browser build with a module string other than the bundled core worker — e.g. a plugin that tries to load its own worker module in a browser context.

Common situations: Browser/web worker Parcel integrations; misconfigured bundling that includes the child worker code; plugins assuming Node dynamic require works in the browser.

Related errors

• No dynamic require possible: ${workerPath}
• No dynamic require possible: ${location}
• IDBCache is only supported in the browser
• Supplied WorkerFarm is ending
• More than one target is not supported in serve mode

AI-assisted analysis of parcel-bundler/parcel@59484858a1 (2026-08-13). Data as JSON: /api/errors/79c8dbc5e6c5384c. Report an issue: GitHub.