Table of Contents

• Introduction: A Decade of Frontend APIs
• The Early Days: XMLHttpRequest (XHR)
• A Simpler Web: The Fetch API
• The Rise of Axios
• Data Fetching Becomes Smarter: SWR & React Query
• The Missing Piece: API Testing & Collaboration
• Bruno: Rethinking the API Workflow
• The Future of Frontend APIs
• Conclusion

Over the past decade, APIs have transformed the way applications are built. What started as simple browser-based requests has evolved into a rich ecosystem of tools, libraries, and workflows focused on performance, developer experience, and scalability.

Let’s take a look at how API interaction has evolved over time and where the ecosystem is heading next.

1. The Early Days: XMLHttpRequest (XHR)

In the early days of web development, XMLHttpRequest (XHR) was the primary way to communicate with APIs from the browser.

While powerful for its time, XHR came with drawbacks:

• Verbose and hard-to-read syntax
• Callback-heavy code
• Poor error handling

// XMLHttpRequest (XHR) example
const xhr = new XMLHttpRequest();
xhr.open("GET", "https://api.example.com/users");
xhr.onload = () => {
  if (xhr.status >= 200 && xhr.status < 300) {
    console.log(JSON.parse(xhr.responseText));
  } else {
    console.error("Error:", xhr.status, xhr.responseText);
  }
};
xhr.onerror = () => console.error("Network error");
xhr.send();

XHR laid the foundation, but developers quickly needed something cleaner and more intuitive.

2. A Simpler Web: The Fetch API

The introduction of the Fetch API marked a big step forward. It provided a promise-based interface that made API calls easier to read and maintain.

Fetch improved developer experience by:

• Using promises instead of callbacks
• Providing a cleaner, modern syntax
• Being built directly into the browser

// Fetch API example
async function getUsers() {
  const res = await fetch("https://api.example.com/users");
  if (!res.ok) throw new Error(`HTTP ${res.status}`);
  const data = await res.json();
  console.log(data);
}
getUsers().catch(console.error);

However, Fetch still required manual handling for common concerns like request cancellation, interceptors, and default headers.

3. The Rise of Axios

Axios became popular by addressing many gaps left by Fetch. It introduced a higher-level abstraction that made API communication more convenient for real-world applications.

Developers adopted Axios for:

• Automatic JSON transformation
• Request and response interceptors
• Better error handling
• Browser and Node.js support

// Axios example
import axios from "axios";

async function getUsers() {
  const res = await axios.get("https://api.example.com/users");
  console.log(res.data);
}
getUsers().catch(console.error);

Axios quickly became a standard choice for frontend and backend API calls.

4. Data Fetching Becomes Smarter: SWR & React Query

As applications grew more complex, API interaction moved beyond simple request-response cycles.

Libraries like SWR and React Query introduced a new way of thinking about API data:

• Automatic caching
• Background revalidation
• Optimistic UI updates
• Focus on data consistency rather than manual fetching

// SWR example
import useSWR from "swr";

const fetcher = (url) => fetch(url).then((r) => r.json());

export function Users() {
  const { data, error, isLoading } = useSWR(
    "https://api.example.com/users",
    fetcher
  );

  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error loading data</div>;

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

// React Query example
import { useQuery } from "@tanstack/react-query";

async function getUsers() {
  const res = await fetch("https://api.example.com/users");
  if (!res.ok) throw new Error(`HTTP ${res.status}`);
  return res.json();
}

export function UsersRQ() {
  const { data, error, isLoading } = useQuery({
    queryKey: ["users"],
    queryFn: getUsers
  });

  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error loading data</div>;

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

APIs were no longer just endpoints — they became part of state management and application behavior.

5. The Missing Piece: API Testing & Collaboration

While API consumption evolved rapidly, testing and collaboration often lagged behind. Many teams relied on heavyweight tools or cloud-dependent workflows that didn’t integrate well with codebases.

Bruno: Rethinking the API Workflow

This is where Bruno brings a fresh perspective to the API space.

Bruno is a local-first, Git-based API client that treats API collections as code. Instead of storing API definitions in proprietary formats or remote servers, Bruno keeps everything in simple, readable files.

Key capabilities include:

• Git-native collaboration using plain files
• Local-first workflow with full offline support
• Scriptable requests and assertions
• Easy integration with CI/CD pipelines

As APIs continue to evolve, tools like Bruno help teams bring the same engineering discipline to API testing and collaboration that they already apply to application code.

Conclusion

From XHR to Fetch, Axios, and modern data-fetching libraries, the past decade has fundamentally reshaped how developers work with APIs.

The next evolution isn’t just about making requests faster, and it’s about building workflows that are local, version-controlled, and developer-first. That’s the direction the API ecosystem is heading.