There’s nothing quite like shaving nearly a second off a Largest Contentful Paint (LCP) score with a single change — especially when that change takes less than an afternoon to implement. That’s what Early Hints can deliver. But as with any new web performance standard, the devil’s in the adoption details. Some browsers embrace them fully, others are still on the sidelines.

The good news? Even if not every browser plays along, Early Hints can still be one of the easiest, highest-ROI optimizations you’ll make this year. Let’s break down where things stand, how to maximize benefits across all users, and what to expect as adoption grows.

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What Early Hints Actually Do

Early Hints use the HTTP 103 status code to tell a browser, “Here’s what you’ll need for this page — start fetching it now, before I send you the HTML.”

Instead of waiting for the full page to arrive before grabbing critical CSS, JavaScript, or hero images, the browser can start pulling them down immediately. This overlap shaves precious milliseconds (or more) off key metrics like Time to First Byte (TTFB) and LCP.

In practice, it’s a tiny payload that makes a big difference, especially on pages with large HTML documents or heavyweight render-blocking assets.

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The State of Browser Support

Here’s the reality check: Chrome, Edge, and Firefox support Early Hints today. Safari on iOS and macOS doesn’t — at least, not yet.

That means a subset of your audience won’t benefit from the HTTP 103 preload magic. But that’s not a reason to skip implementation.

1. Most traffic is already on supportive browsers — In many markets, Chrome alone accounts for more than half of desktop and mobile browsing.
2. The gains are immediate for supported browsers — You don’t need 100% coverage to see meaningful real-world improvements in your Core Web Vitals.
3. The fallback is already in your toolkit — Browsers without Early Hints support will still respond to preload and preconnect headers in your HTML.
   
   

In other words, this isn’t an all-or-nothing scenario. It’s a progressive enhancement.

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Building for Mixed Support

When browser adoption is uneven, the trick is to plan for the lowest common denominator without sacrificing performance.

Here’s how to do it:

• Serve Early Hints where they’re supported — Use your CDN or application layer to inject 103 responses for critical assets.
• Mirror those hints in HTML headers — For unsupported browsers, preload and preconnect tags high in your HTML still accelerate resource fetching.
• Target only the assets that matter most — Over-hinting everything dilutes the benefit. Focus on LCP images, render-blocking CSS, and must-have JavaScript.

By combining Early Hints with intelligent HTML fallbacks, you cover all users while still unlocking the most significant gains for those who can take advantage.

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Measuring in the Real World

One trap teams fall into is relying solely on lab tools like Lighthouse to measure the impact. Lighthouse is great for controlled testing, but it doesn’t tell you how actual users experience your site in the wild.

For Early Hints, that difference matters:

• Lab (Lighthouse) will show how Early Hints impact your metrics in a single, idealized scenario.
• RUM (Real User Monitoring) will reveal how those gains play out across devices, networks, and geographies — and whether specific user segments benefit more.

Look at both. Use Lighthouse to validate your implementation, then use RUM to quantify the ROI across your actual user base.

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Why It’s Worth Doing Now

Could you wait until Safari catches up? Sure. But that’s like refusing to install faster broadband because your neighbor hasn’t upgraded yet.

The performance arms race is constant. Every millisecond you save is another step ahead of your competitors in engagement, conversion, and user satisfaction. And with an implementation path that’s straightforward, often just a tweak to your CDN configuration and a data source for your hints, it’s one of the lowest-effort, highest-reward optimizations available.

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The Road Ahead

Browser support for new performance features rarely moves in lockstep, but adoption almost always grows over time. In the meantime, Early Hints already deliver measurable wins for a majority of users, without breaking anything for the rest.

That’s the sweet spot in performance engineering: a change that’s simple to ship, safe to deploy, and impactful from day one. The sooner you put it in place, the sooner you start reaping those milliseconds, and the revenue, retention, and trust they bring with them.Need help implementing Early Hints? We’re happy to help.