Early Hints

Early Hints

Hints; often hailed as the guiding beacons to success, do not always take the form we expect. In web technology, they manifest in innovative ways, significantly altering how we interact with and experience the digital world. 

One such transformative concept is "Early Hints," a term that, while technical, holds the promise of revolutionizing web performance and user experience. It's a concept that, at its core, seeks to optimize the way browsers and servers communicate, laying the groundwork for a faster web browsing experience.

What is Early Hints?

Early Hints is an innovative protocol introduced as part of HTTP, specifically denoted as the 103 Early Hints status code. This feature is designed to enhance the efficiency of web page loading. Traditionally, when a browser requests a web page, it waits for the server to process the request and send back the necessary resources. 

Early Hints changes this dynamic by allowing the server to send preliminary responses, hinting at what resources will be needed for the page. This means that even before the server has fully processed the request, the browser can start loading certain elements, such as CSS files, JavaScript, and images.

The concept of Early Hints aligns with the modern web's need for speed and efficiency. In a digital ecosystem where every second counts, reducing the time it takes for a page to become interactive and visually complete is the baseline.


How Do Early Hints Work?

Early Hints is an HTTP status code - 103. When a browser requests a webpage, it initiates an HTTP transaction with the server hosting the webpage. In standard operations, the server processes this request and sends back a complete HTTP response, usually starting with a status code like 200 (OK) followed by the requested content.

However, with Early Hints, the server interjects an additional step. Before sending the final response, the server sends a 103 Early Hints status code. This preliminary response is lightweight and contains ‘Link’ headers. These headers are essentially pre-emptive signals, indicating which resources (CSS, JavaScript files, images, etc.) the server will likely send in the final response.

Preloading at its Finest!

The technical brilliance of Early Hints lies in its utilization of these Link headers. Browsers like Chrome interpret these headers and start fetching the specified resources in advance. This is done using resource hints such as <link rel="preload"> in the HTML or through headers themselves. 

Preloading resources means the browser initiates connections, performs DNS lookups, and even starts downloading resources before the server has completed processing the full request.

On the server side, implementing Early Hints involves configuring the server software (like Apache, Nginx) to recognize situations where Early Hints can be beneficial and configuring it to send the appropriate Link headers.

Benefits of Early Hints

While some of these are already apparent at first glance, preloading resources can launch a chain effect of interlined benefits, making it a non-negotiable option:

a. Enhanced Web Performance and User Experience:

  1. Significant reduction in perceived load times for web pages.
  2. Improves the "time to first paint" metric, leading to faster content display.
  3. Crucial for enhancing user experience in a digital landscape where speed is key.
  4. Reduces user frustration and bounce rates by ensuring quicker response and smoother browsing.

b. Amplified Benefits for Complex Websites and SEO Rankings:

  1. Especially beneficial for websites with large images, elaborate stylesheets, and extensive JavaScript files.
  2. Preemptive loading of resources reduces the impact of latency, particularly for cross-origin resources.
  3. Enhances user experience and contributes to better search engine optimization (SEO).
  4. Faster loading times are favored by search engines, potentially leading to higher website rankings.

c. Server Efficiency and Network Optimization:

  1. Contributes to a more balanced server load, especially during high traffic periods.
  2. Optimizes network utilization by preloading resources while the server processes requests.
  3. Prevents bursts of resource requests following the final response, leading to more efficient server operation.
  4. Results in a more efficient use of network resources and bandwidth.


Implementation of Early Hints

This approach to implementing Early Hints leverages the "server think-time" to asynchronously instruct the browser to begin loading critical resources, thereby improving page load times and reducing perceived latency for users.

1. Evaluate the Necessity of Early Hints

Firstly, assess if your server can immediately serve a main 200 response upon receiving a request. If it can, implementing Early Hints may not be necessary, as both 103 and 200 responses could be sent simultaneously, rendering Early Hints redundant. 

In such cases, using the Link Header directly in the main HTTP Response Header or using the <link> element in your HTML's <head> section could suffice for tasks like preload and preconnect.

2. Server Compatibility and Configuration

For servers that require time to process requests (hence benefiting from Early Hints), it's crucial to ensure your server software supports Early Hints. Apache and H2O HTTP servers, for instance, support Early Hints.

In Apache, enable Early Hints using mod_http2 with the directive H2EarlyHints on. Then, use H2PushResource to send Early Hints for specific resources.

In H2O, Early Hints can be implemented using header directives with when: early or through mruby scripting.

3. Utilizing CDNs for Early Hints

Implementing Early Hints through a Content Delivery Network (CDN) like Cloudflare or Fastly can be an efficient approach, especially for static resources like CSS and JavaScript. 

CDNs can convert resource hints in your code to Early Hints automatically.

Bonus: Tips To Remember

  1. Identify top landing pages where users typically start their journey on your site, as Early Hints are most effective on these initial entry points.
  2. Determine critical origins and sub-resources that contribute significantly to key performance metrics like Largest Contentful Paint or First Contentful Paint. Focus on render-blocking resources such as synchronous JavaScript, stylesheets, or web fonts.
  3. Be cautious with resources that are frequently updated or versioned, as they may not be ideal candidates for Early Hints. Aim for stable resources and origins, independent of the outcome for the main resource.
  4. Consider splitting key resources into a stable part for Early Hints and a more dynamic part for later fetching.
  5. On receiving a request from a supported browser, the server should immediately respond with 103 Early Hints, including relevant preconnect and preload hints. Follow this with the usual response (e.g., 200 OK) once the main resource is ready.


This advanced protocol, integral to the HTTP framework and symbolized by the 103 Early Hints status code, has revolutionized the traditional dynamics of web page loading. By enabling servers to send preliminary responses about needed resources, Early Hints facilitates a more efficient and rapid loading process for web pages. 

This forward-thinking approach is not only about speeding up the loading times but also about optimizing the interaction between browsers and servers, setting a new standard for what users can expect from their web browsing experience.

Published on:
January 31, 2024
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