HTML中的<base>標(biāo)籤用於為文檔中所有相對URL指定一個基礎(chǔ)URL，它會影響鏈接、圖片、腳本和樣式表等資源的解析方式。例如設(shè)置後，會從https://example.com/assets/image.jpg加載。此外，<base>還支持target屬性來定義鏈接默認(rèn)打開方式，如使鏈接在新標(biāo)籤頁打開。但需要注意：1. <base>必須放在

中且位於其他引用URL元素之前；2. 若單個鏈接有自定義target屬性，則會覆蓋base設(shè)定；3. 在動態(tài)網(wǎng)站、混合使用絕對/相對URL或可複用模板中應(yīng)謹(jǐn)慎使用。

The <base> tag in HTML is used to define a base URL for all the relative URLs in a document. It's one of those tags that many people skip over or forget, but it can be really useful — or even tricky — if you're not aware of how it works.

How <base> Affects Links and Resources

When you set a <base> tag in your HTML document's , every relative URL inside that document will resolve based on the value of the href attribute in <base> . This includes links ( <a></a> ), images ( <img alt="文檔中標(biāo)籤的目的是什麼？" > ), scripts ( <script></script> ), stylesheets ( <link> ), and more.

For example:

 <base href="https://example.com/assets/">
<img  src="/static/imghw/default1.png"  data-src="image.jpg"  class="lazy" alt="文檔中標(biāo)籤的目的是什麼？" > <!-- Actually loads from https://example.com/assets/image.jpg -->

This can help simplify development if resources are always in a specific directory. But beware: once set, it affects all relative URLs , so you need to make sure your paths align with this base.

Also, if you're linking internally using relative paths and you change the base URL, those links might point somewhere unexpected.

You Can Also Set a Default Target

In addition to the href attribute, the <base> tag supports a target attribute. This sets the default browsing context (like a tab or window) for all links in the document.

For example:

 <base target="_blank">
<a href="https://example.com">Open Example</a>
<!-- This link will open in a new tab by default -->

You won't see this used often, but it can be handy in documentation sites or apps where external links should consistently open in a new tab without repeating the target="_blank" on every link.

Just keep in mind:

• The target only applies to elements that have a target attribute (mostly links).
• If a specific link has its own target , it overrides the base setting.

Placement Matters

One important thing: the <base> tag must appear inside the section and should come before any other elements that use URLs , like <link> or <script></script> . Otherwise, some browsers might ignore it or apply it inconsistently.

So putting it near the top of your ensures that all following relative URLs are resolved correctly.

When Not to Use <base>

While it can be helpful, there are cases when it's better to avoid it:

• In dynamic websites where content moves between environments (dev, staging, prod), because it can cause confusion if not updated.
• If you're mixing relative and absolute URLs heavily, since it adds another layer of indirection.
• In templates or components that might be reused elsewhere — relying on a base URL can break assumptions.

In short, it's a powerful tool, but needs to be handled carefully.

基本上就這些。

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