🐛 Bug: React useEffect causes duplicate API requests in development

[kdva-code]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Code quality

Discussion Details

Description

I've noticed that an API request inside useEffect can execute twice when running a React application in development mode with React.StrictMode enabled.

Consider this example:

import { useEffect, useState } from "react";

function Users() {
  const [users, setUsers] = useState([]);

  useEffect(() => {
    fetch("/api/users")
      .then((res) => res.json())
      .then(setUsers);
  }, []);

  return (
    <ul>
      {users.map((user) => (
        <li key={user.id}>{user.name}</li>
      ))}
    </ul>
  );
}

export default Users;

Application entry point:

import React from "react";
import ReactDOM from "react-dom/client";
import Users from "./Users";

ReactDOM.createRoot(document.getElementById("root")).render(
  <React.StrictMode>
    <Users />
  </React.StrictMode>
);

Expected Behavior

The component should fetch the users without causing unnecessary duplicate network requests.

Actual Behavior

In development mode, React StrictMode performs an additional setup and cleanup cycle for Effects. As a result, the effect above can trigger two GET requests.

This behavior does not normally occur in the same way in production builds.

Possible Solution

One approach is to use AbortController to cancel the previous request during cleanup:

useEffect(() => {
  const controller = new AbortController();

  fetch("/api/users", {
    signal: controller.signal,
  })
    .then((res) => res.json())
    .then(setUsers)
    .catch((error) => {
      if (error.name !== "AbortError") {
        console.error(error);
      }
    });

  return () => controller.abort();
}, []);

Questions

1. Is this the recommended approach for handling duplicate requests in React StrictMode?
2. Would using TanStack Query or another data-fetching library be a better solution?
3. Should developers handle this at the component level or centralize request management?

Environment:

• React 18+
• Development mode
• React.StrictMode enabled

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[hexjasur]

I think using AbortController is a good approach for handling this particular case, especially when working with native fetch().

However, I wouldn't consider it a complete solution for every duplicate request scenario.

React StrictMode intentionally runs an additional Effect setup and cleanup cycle in development to help identify missing cleanup logic. So disabling StrictMode just to avoid duplicate requests isn't really the right fix.

For larger applications, I'd prefer using TanStack Query because it provides request deduplication, caching, automatic retries, and better control over server state.

My recommendation:

• Use AbortController for simple component-level requests.
• Use TanStack Query when multiple components share server data.
• Always implement proper cleanup in Effects.
• Don't disable StrictMode just to hide the issue.

One important detail: aborting a request doesn't guarantee that the server never received or processed it. This is especially important for POST, PUT, and other non-idempotent operations.

[hexjasur]

.