The <base> tag in HTML is used to specify a base URL for all relative URLs in a document, which will affect the parsing of resources such as links, images, scripts, and stylesheets. For example, after setting will be loaded from https://example.com/assets/image.jpg. In addition, <base> also supports the target attribute to define the default opening method of links, such as
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="What is the purpose of the tag in the document ?" >
), 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="What is the purpose of the tag in the document ?" > <!-- 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 browser 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 atarget
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.
Basically that's it.
The above is the detailed content of What is the purpose of the tag in the document ?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

HTML5isbetterforcontrolandcustomization,whileYouTubeisbetterforeaseandperformance.1)HTML5allowsfortailoreduserexperiencesbutrequiresmanagingcodecsandcompatibility.2)YouTubeofferssimpleembeddingwithoptimizedperformancebutlimitscontroloverappearanceand

inputtype="range" is used to create a slider control, allowing the user to select a value from a predefined range. 1. It is mainly suitable for scenes where values ??need to be selected intuitively, such as adjusting volume, brightness or scoring systems; 2. The basic structure includes min, max and step attributes, which set the minimum value, maximum value and step size respectively; 3. This value can be obtained and used in real time through JavaScript to improve the interactive experience; 4. It is recommended to display the current value and pay attention to accessibility and browser compatibility issues when using it.

The way to add drag and drop functionality to a web page is to use HTML5's DragandDrop API, which is natively supported without additional libraries. The specific steps are as follows: 1. Set the element draggable="true" to enable drag; 2. Listen to dragstart, dragover, drop and dragend events; 3. Set data in dragstart, block default behavior in dragover, and handle logic in drop. In addition, element movement can be achieved through appendChild and file upload can be achieved through e.dataTransfer.files. Note: preventDefault must be called

AnimatingSVGwithCSSispossibleusingkeyframesforbasicanimationsandtransitionsforinteractiveeffects.1.Use@keyframestodefineanimationstagesforpropertieslikescale,opacity,andcolor.2.ApplytheanimationtoSVGelementssuchas,,orviaCSSclasses.3.Forhoverorstate-b

Audio and video elements in HTML can improve the dynamics and user experience of web pages. 1. Embed audio files using elements and realize automatic and loop playback of background music through autoplay and loop properties. 2. Use elements to embed video files, set width and height and controls properties, and provide multiple formats to ensure browser compatibility.

WebRTC is a free, open source technology that supports real-time communication between browsers and devices. It realizes audio and video capture, encoding and point-to-point transmission through built-in API, without plug-ins. Its working principle includes: 1. The browser captures audio and video input; 2. The data is encoded and transmitted directly to another browser through a security protocol; 3. The signaling server assists in the initial connection but does not participate in media transmission; 4. The connection is established to achieve low-latency direct communication. The main application scenarios are: 1. Video conferencing (such as GoogleMeet, Jitsi); 2. Customer service voice/video chat; 3. Online games and collaborative applications; 4. IoT and real-time monitoring. Its advantages are cross-platform compatibility, no download required, default encryption and low latency, suitable for point-to-point communication

To confirm whether the browser can play a specific video format, you can follow the following steps: 1. Check the browser's official documents or CanIuse website to understand the supported formats, such as Chrome supports MP4, WebM, etc., Safari mainly supports MP4; 2. Use HTML5 tag local test to load the video file to see if it can play normally; 3. Upload files with online tools such as VideoJSTechInsights or BrowserStackLive for cross-platform detection. When testing, you need to pay attention to the impact of the encoded version, and you cannot rely solely on the file suffix name to judge compatibility.

The key to using requestAnimationFrame() to achieve smooth animation on HTMLCanvas is to understand its operating mechanism and cooperate with Canvas' drawing process. 1. requestAnimationFrame() is an API designed for animation by the browser. It can be synchronized with the screen refresh rate, avoid lag or tear, and is more efficient than setTimeout or setInterval; 2. The animation infrastructure includes preparing canvas elements, obtaining context, and defining the main loop function animate(), where the canvas is cleared and the next frame is requested for continuous redrawing; 3. To achieve dynamic effects, state variables, such as the coordinates of small balls, are updated in each frame, thereby forming
