How to Fix Queuemicrotask Error in React

Encountering a queuemicrotask error while working with React? This guide covers the root cause, provides a working code example, and shows you how to prevent it from recurring.

What's Happening

queueMicrotask is a modern Web API for scheduling microtasks that run after the current task completes but before the browser yields control. The error in React typically occurs when:

• Code runs in an environment where queueMicrotask isn't defined (older browsers, certain SSR contexts, or test runners)
• A third-party library calls queueMicrotask internally, expecting it to exist globally
• Server-side rendering encounters browser-only APIs

The Solution

Add a polyfill or use a safe wrapper pattern:

// Polyfill for environments without queueMicrotask
if (typeof queueMicrotask !== "function") {
  const resolved = Promise.resolve();
  globalThis.queueMicrotask = (callback) => {
    resolved.then(callback).catch((err) =>
      setTimeout(() => {
        throw err;
      }, 0)
    );
  };
}

// Safe usage in a React component
import { useEffect, useState } from "react";

function DataProcessor({ rawData }) {
  const [processed, setProcessed] = useState(null);

  useEffect(() => {
    // Schedule processing as a microtask
    queueMicrotask(() => {
      const result = expensiveTransform(rawData);
      setProcessed(result);
    });
  }, [rawData]);

  return processed ? <Display data={processed} /> : <Loading />;
}

When to Use queueMicrotask

• Batching state updates that must happen before the next paint
• Deferring computation without yielding to the browser's macro task queue
• Running cleanup logic that must execute before subsequent microtasks

In most cases, Promise.resolve().then(callback) achieves identical timing semantics and has broader compatibility.

Testing Considerations

If your test runner doesn't provide queueMicrotask, add the polyfill in your test setup file to avoid false failures.

Track microtask-related errors and environment compatibility gaps with [Bugsly](https://bugsly.dev) — see exactly which browsers and runtimes trigger the issue.