What are the key differences between HTML4 and HTML5?

HTML5 has significantly improved semantic tags, multimedia support, form functionality and local storage compared to HTML4. 1. HTML5 introduces more semantic tags such as

The difference between HTML4 and HTML5 is actually quite obvious, especially in terms of function extension, tag semantics and support for modern web page requirements. HTML5 has been optimized and enhanced in many aspects, making development more efficient and more suitable for the current Web development.

1. Clearer semantic tags

HTML4 uses mostly common tags, such as <div> and <code><span></span> to divide page structure, while HTML5 introduces more descriptive tags, such as:

• <header></header> means the header of the page
• <nav></nav> means navigation bar
• <article></article> means independent content block
• <section></section> means content block
• <footer></footer> means bottom information

These tags not only make the code easier to understand, but also help aid tools such as SEO and screen readers to better parse page structure.

2. Natively support multimedia elements

In HTML4, embedding audio or video often requires relying on third-party plugins (such as Flash), and HTML5 provides native support:

• <audio></audio> tags can be inserted directly into audio files
• <video></video> tag can play videos, and it also supports control bars, automatic playback and other functions.

The advantage of this is that there is no need to introduce additional plugins, which improves compatibility and loading speed, especially on mobile devices.

3. Form input type and verification enhancement

HTML5 supports forms more powerfully, and has added many new input types, such as:

• <input type="email"> Email format verification
• <input type="date"> Date selector
• <input type="number"> Number input box
• <input type="search"> Search box style optimization

At the same time, HTML5 also provides a simple client verification mechanism, such as required attribute, which allows the browser to check whether the content has been filled in before submitting, reducing JavaScript dependency.

4. Offline applications and local storage support

HTML5 introduces Application Cache and local storage mechanisms (localStorage and sessionStorage), so that web pages can continue to run without a network connection, and data can be retained after the user closes the page. This is very useful when developing web applications, such as making some offline notes, caching resources, etc.

In contrast, HTML4 has almost no ability in this area and can only rely on cookies to store a small amount of data, and it will be carried with you every time you request it, which is not very efficient.

Basically these key differences. HTML5 not only simplifies the development process, but also improves user experience and performance, which is the main reason why it gradually replaces HTML4.