Boosting LCP: A Guide to fetchpriority='high'

Source: Dev.to

What is fetchpriority?

fetchpriority is a browser hint that signals the relative importance of a resource. While browsers are generally good at guessing what to load first, they aren’t psychic. By adding fetchpriority="high" you move a critical asset to the front of the loading queue.

When a browser parses a page it assigns a priority level (Low, Medium, High, or Very High) to each resource:

• Images: usually Low or Medium
• Scripts and CSS: usually High

Manually setting the priority overrides these defaults, ensuring that “hero” elements don’t get stuck behind less critical tasks.

Impact on Largest Contentful Paint (LCP)

LCP measures when the largest image or text block becomes visible. If your hero image is the LCP element, fetchpriority="high" can:

• Reduce queueing time – the browser starts downloading the image sooner.
• Optimize bandwidth – more network “pipe” is allocated to that asset.
• Improve UX – users see the main content faster, reducing bounce rates.

Real‑world tests have shown LCP improvements of 20‑30 % when the attribute is applied correctly.

How to Use fetchpriority

Images

[Image: New Summer Collection]

Preloading Critical Assets

Lowering Priority for Non‑Critical Resources

[Image: Secondary image]

General Guidelines

• Don’t overdo it – if everything is marked “high,” the hint loses meaning. Use it for the 1‑2 most critical elements above the fold.
• Combine with lazy loading – apply fetchpriority="high" to top‑of‑page assets and loading="lazy" to everything else. Never use both on the same image.

Testing the Hint

Open Chrome DevTools → Network tab and enable the Priority column. You’ll see the priority assigned to each request, allowing you to verify that your hints are being respected.

Conclusion

fetchpriority="high" is a simple yet powerful tool in a developer’s performance toolkit. It isn’t a magic wand, but it acts as a loud megaphone that tells the browser to focus on what truly matters to your users.