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The Impact of 103 Early Hints on Web Development - HTTP Status Code

Anchal Rastogi
~ 6 min read | Published on Mar 28, 2024


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What is a 103 status code?

HTTP status codes are crucial elements of communication between a client (such as a web browser) and a server. They convey information about the outcome of a request made by the client. Among these status codes, the 103 status code is relatively new and serves a specific purpose in web development.

A 103 Early Hints status code is used by servers to send some HTTP headers before the final HTTP response. This allows the client to start processing the response before it's fully available. Essentially, it hints at the eventual response headers and allows the client to start fetching resources while the server is still preparing the complete response. This can significantly improve performance by reducing latency.

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What are the possible use cases for 103 status code?

Preloading Resources:

One of the primary use cases for the 103 status code is resource preloading. By sending hints about necessary resources, such as CSS files, JavaScript libraries, or images, the server enables the client to start fetching these resources in parallel with processing the main response. This can result in faster page rendering times.

Pushing Critical Resources:

For web applications that require high performance, critical resources can be pushed to the client using the 103 status code. This ensures that essential assets are delivered promptly, reducing loading times and improving user experience.

Server Push for HTTP/2:

In environments where HTTP/2 is used, the 103 status code can initiate server push. Server push allows the server to proactively send resources to the client before they are requested, further optimizing performance by reducing round-trip times.

How to implement 103 status code in JavaScript?

Implementing the 103 status code involves configuring the server to send early hints. While the specifics depend on the server technology being used, here's a basic example of how it can be achieved using Node.js and Express:

const express = require('express');
const app = express();

app.use((req, res, next) => {
  res.set('Link', '</styles.css>; rel=preload; as=style, </script.js>; rel=preload; as=script');

app.listen(3000, () => {
  console.log('Server is running on port 3000');

In this example, the server is configured to send preloading hints for two resources (styles.css and script.js) using the Link header. It then sends the 103 status code to indicate that early hints have been provided.

Best Practices for using 103 status code

Provide Relevant Hints:

Ensure that the hints sent with the 103 status code are relevant to the resources required for rendering the page. Sending unnecessary hints can increase overhead without providing significant performance benefits.

Optimize Resource Delivery:

Use tools and techniques to optimize the delivery of resources hinted with the 103 status code. This may include minification, compression, and caching strategies to further reduce latency and improve load times.

Monitor Performance:

Regularly monitor the performance of your web application to assess the impact of using the 103 status code. Analyze metrics such as page load times, resource fetch times, and server response times to identify areas for optimization.

How to test 103 status code on Postman?

Testing the 103 status code in Postman involves sending a request to a server that is configured to respond with this status code along with early hints. Here's how you can do it:

  1. Open Postman and create a new request.
  2. Enter the URL of the server that supports the 103 status code.
  3. Send the request.
  4. Check the response headers to verify that the server is sending early hints with the 103 status code.

How to test 103 status code in DevTools browser in Chrome?

To test the 103 status code in Chrome DevTools:

  1. Open Chrome and navigate to the website you want to test.
  2. Open DevTools by right-clicking on the page and selecting "Inspect" or pressing Ctrl + Shift + I.
  3. Go to the "Network" tab.
  4. Refresh the page.
  5. Look for the request/response that returns a status code of 103.
  6. Inspect the response headers to confirm the presence of early hints.

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Frequently Asked Questions

Q: Can the 103 status code be used with any HTTP version?

A: No, the 103 status code is specifically designed for HTTP/2 and later versions. It is not supported in HTTP/1.1.

Q: Does using the 103 status code guarantee performance improvements?

A: While the 103 status code can potentially improve performance by allowing the client to start fetching resources early, its effectiveness depends on various factors such as network conditions, server configuration, and the nature of the web application.

Q: Are there any downsides to using the 103 status code?

A: One potential downside is increased server overhead due to the need to send additional headers. Additionally, improper use of the 103 status code or sending irrelevant hints can degrade performance rather than improve it.

Q: How do browsers handle responses with the 103 status code?

A: Browsers that support the 103 status code will process the early hints and start fetching the hinted resources in parallel with processing the main response. This can result in faster page rendering times.

Q: Can the 103 status code be used for non-resource hints?

A: While the primary use case for the 103 status code is resource preloading, it can theoretically be used to provide hints for other types of information needed for processing the response, such as cache directives or security headers.


In the fast-paced world of web development, optimizing performance is paramount. The introduction of the 103 Early Hints status code offers developers a powerful tool for improving page load times and enhancing user experience. By providing hints about critical resources, servers can enable clients to start fetching necessary assets sooner, resulting in faster rendering times and smoother interactions.

For developers seeking to harness the potential of the 103 status code and streamline error monitoring and handling processes, tools like Zipy offer invaluable assistance. Zipy provides comprehensive error monitoring capabilities coupled with session replay functionality, allowing developers to pinpoint and resolve issues with ease. To learn more about Zipy and how it can elevate your error handling strategy, visit

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