rel="preload"用于立即加載當前頁面關(guān)鍵資源，如字體或腳本；而rel="prefetch"則用于在空閑時預(yù)加載未來可能需要的資源，如后續(xù)頁面內(nèi)容。1. rel="preload"通過標簽指定關(guān)鍵資源提前下載，適用于對首屏渲染至關(guān)重要的文件，并需配合as、crossorigin等屬性使用；2. rel="prefetch"用于提升后續(xù)導(dǎo)航性能，常用于預(yù)加載用戶可能訪問的下一頁資源，優(yōu)先級較低，適合廣泛使用；3. 使用時應(yīng)避免濫用preload導(dǎo)致當前頁面變慢，或prefetch頻繁變化的內(nèi)容造成資源浪費。兩者應(yīng)根據(jù)實際場景選擇，以優(yōu)化加載性能。

Resource hints like rel="preload" and rel="prefetch" are HTML attributes used to tell the browser how to handle resource loading in advance, helping improve page performance. Their main purpose is to give developers more control over how and when resources (like fonts, scripts, or images) are fetched by the browser.

Here’s a closer look at what each does and when you might use them.

What rel="preload" is for

rel="preload" tells the browser that a certain resource is needed right now, so it should start downloading it as soon as possible. This is useful for critical resources that are essential for rendering the current page.

For example, if you have a font file that your site uses right away, but it's loaded through CSS (which the browser might not detect early enough), using preload ensures it gets downloaded sooner rather than later.

<link rel="preload" href="myfont.woff2" as="font" type="font/woff2" crossorigin>

Key points:

• Use as attribute to help the browser understand what kind of resource it is.
• Always include crossorigin for fonts, even if they're on the same domain.
• Don't overuse it — only preload truly critical resources.

How rel="prefetch" works differently

rel="prefetch" is more about preparing for the future. It tells the browser to fetch a resource in the background when there's free bandwidth, usually for pages the user might navigate to next.

It’s commonly used for links that users are likely to click, like the next page in a multi-step form or article series.

<link rel="prefetch" href="/next-page.html">

Some things to keep in mind:

• Prefetched resources are low priority, so they won’t interfere with current page loading.
• Works well for DNS lookups (dns-prefetch) or preloading full pages (prerender in some browsers).
• Less aggressive than preload, which makes it safer to use more broadly.

When to choose one over the other

The key difference comes down to timing and intent:

• Use preload for current page needs — things that must be ready as the page loads.
• Use prefetch for future navigation — resources that may be needed later, especially after user interaction.

Examples of misuse:

• Preloading too many assets can slow down the current page.
• Prefetching something that changes often (like personalized content) might waste effort.

So think carefully about what you’re hinting to the browser — not every asset needs a hint.

Basically, these tools help fine-tune performance, but they work best when applied selectively and thoughtfully.

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