HTML structure has an important impact on page loading performance, which is mainly reflected in four aspects: First, reduce the number of DOM nodes, avoid unnecessary packaging elements and excessive use of semantic tags, and merge duplicate structures to improve parsing efficiency; Second, control the size of HTML files, and automatically optimize the structure by compressing output, avoiding inline large amounts of data, and using frameworks to automatically optimize the structure; Third, load key resources in advance, such as inline key CSS, controlling script loading with defer or async attributes, and use preload to prioritize important files; Fourth, keep the structure clear, use the title level reasonably, prefix the main content, and reduce dynamic insertion of JS to optimize SEO and first-screen rendering.

Although HTML structure itself does not directly occupy a large amount of loading resources like images or scripts, its impact on page loading performance is actually much more important than many people think. A reasonable HTML organization method can improve browser parsing efficiency, speed up the first-screen rendering speed, and even indirectly affect the optimization of key rendering paths.

Reduce the number of DOM nodes

The more DOM (Document Object Model) nodes, the longer it takes for the browser to parse and render. Especially HTML with deep nesting hierarchies and complex structures will increase memory consumption and slow down JavaScript operations.

• Avoid unnecessary packaging elements (such as multiple <div> that do not work)<li> When using semantic tags, you should also be moderate. For example, <code><section></section> , <article></article> , etc. are good, but they should not be overused.
• Merge duplicate structures. For example, if list items can be processed in a unified manner, do not write multiple block-level elements separately.

For example: If you use 50 nested <div> to layout a simple card component, it is definitely not as efficient as adding a <code><section></section> to a few necessary child elements.

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Control HTML file size

Although the HTML page itself is usually not large in size, it may also become bloated if it contains a large number of redundant comments, spaces, and duplicate code generated dynamically on the server.


• Compress HTML output (remove whitespace, comments, etc.)
• Avoid inlining large amounts of data in HTML (such as JSON data being written directly into the page)
• Automatically optimize output structure using server-side templates or static generation tools

For example, when building static sites, using frameworks like Gatsby or Next.js will help you with HTML compression and structure optimization by default to reduce unnecessary content.

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Loading key resources in advance

HTML is the starting point for the browser to start loading other resources (such as CSS, JS, and images). By reasonably scheduling the reference order of resources in HTML, the browser can help load key content as early as possible.

• Inline the critical CSS in to avoid blocking rendering
• Use defer or async attribute to control script loading time
• Use <link rel="preload"> to load fonts and key JS/CSS files in advance

For example:

 <link rel="preload" href="main.css" as="style" onload="this.rel=&#39;stylesheet&#39;">

This allows the browser to know that this style sheet is important and should be loaded first.

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Keep structure clear, aiding SEO and rendering optimization

Search engine crawlers and browser rendering engines will rely on the HTML structure to judge the importance and order of page content. If the HTML structure is chaotic, it may affect the search engine crawling effect and will also cause the browser to fail to correctly recognize the content on the first screen.

• Using the correct title hierarchy (H1 → H2 → H3) is not only conducive to SEO, but also helps with barrier-free access
• Put the main content in front of HTML, not behind a bunch of ads or sidebars
• Avoid relying too much on JS to dynamically insert main content, otherwise it may cause the first time to load the "white screen" too long

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In general, the impact of HTML structure on performance is fundamental. Although it is not as immediate as compressing images or splitting JS, it is an important part of optimizing the entire page loading process.
Basically that's it.