Strict Mode

• StrictMode is a tool for highlighting potential problems in an application.

• StrictMode does not render any visible UI.

• StrictMode only checks its descendants.

const ExampleApplication = () => (
  <div>
    <Header />
    <React.StrictMode>
      <ComponentOne />
      <ComponentTwo />
    </React.StrictMode>
    <Footer />
  </div>
);

Identifying unsafe lifecycles

Certain legacy lifecycle methods are unsafe for use in async React applications. When strict mode is enabled, React logs a warning message with information about the components using the unsafe lifecycles.

Detecting legacy context API

The legacy context API is error-prone, and will be removed in a future major version.