When building React applications that interact with APIs, you often make HTTP requests from multiple components. Rather than repeating configuration for each request, you can create a custom Axios instance with shared settings such as the baseURL and default headers. This approach ensures consistency and reduces duplication in your codebase.

To create a custom Axios instance, you import Axios and use the axios.create() method. You can specify a baseURL that all requests using this instance will use, and set default headers like authentication tokens or content types. For example, you might define an instance in a separate file, then import and use it in your components for all API calls. This not only keeps your code DRY (Don't Repeat Yourself) but also makes it easier to update configuration in a single place if your API changes.

A typical setup might look like this:

import axios from "axios";

const api = axios.create({
  baseURL: "https://api.example.com",
  headers: {
    "Authorization": "Bearer YOUR_TOKEN",
    "Content-Type": "application/json"
  }
});

export default api;

You can then import api in your React components and use it just like the default Axios instance, but with your global settings already applied.

It is important to understand when to use global configuration like a custom Axios instance versus setting options per request. Global configuration is ideal when most of your requests share common settings, such as the same API endpoint or authentication headers. This approach makes your code cleaner and easier to maintain. However, if you have requests that need unique headers, timeouts, or other settings that differ from the defaults, you can always override the global configuration by specifying options directly in the individual request. This flexibility allows you to balance consistency with customization, depending on the needs of your application.