The viewport meta tag is used to control how web pages are displayed on mobile devices and ensure that the pages are adapted to the screen. Its core function is to prevent the browser from rendering the page with desktop width, making the text too small and the layout compact. The correct way to set it is to add <meta name="viewport" content="width=device-width, initial-scale=1"> in the HTML
, where width=device-width sets the page width equal to the device width, and initial-scale=1 sets the initial scaling ratio to 1. Optional parameters include maximum-scale limiting maximum magnification, user-scalable control whether manual scaling is allowed, but disabling scaling is not recommended. Common problems include fixed-width layout, third-party plug-ins affect responsive design, wrong setting of scaling parameters, etc. The key to the solution lies in the overall adoption of responsive design principles.The viewport meta tag in HTML is a key element used to control how web pages are displayed on mobile devices. Simply put, it tells the phone browser how to scale and resize the page to fit the screen.

Why do mobile terminals need to set viewport?
When you open a web page on your phone that does not set the viewport correctly, the browser usually uses "desktop width" to render the page (such as 980px) and then narrows the page and displays it on the screen. The result is that the text is too small and the layout is compact, and users must manually enlarge it to see the content clearly.

After setting up a suitable viewport, the web page can be adapted according to the actual screen size of the device, providing a more friendly browsing experience.
How to use the viewport meta tag correctly?
The basic way to write viewport is to add the following code to the area of ??HTML:

<meta name="viewport" content="width=device-width, initial-scale=1">
Here are two key parameters:
-
width=device-width
: Make the width of the page equal to the screen width of the device. -
initial-scale=1
: Set the initial scaling ratio to 1 to ensure that the page is not automatically scaled.
You can also add some extra options, such as:
-
maximum-scale=1
: limits the maximum enlargement of the user. -
user-scalable=no
: prohibits user scaling manually (but this is generally not recommended).
These settings can be flexibly combined according to website needs, but in most cases it is just to keep it simple.
Frequently Asked Questions and Precautions
Sometimes even if the viewport tag is added, the page still displays an exception. Common reasons include:
- There is a fixed width layout in the page (such as width: 960px is set), which will make it impossible to adapt on small screens.
- Third-party ads or plug-ins ignore responsive design, destroying the overall layout.
- The maximum-scale or user-scalable is set incorrectly, affecting the user experience.
The key to solving these problems is to ensure that the entire page adopts responsive design principles, rather than just adding a viewport tag.
Basically that's it. Although viewport is just a line of code in HTML, it is crucial for mobile display. Many people tend to ignore it at the beginning, and they don’t check it until the page looks weird on their phones. In fact, just remember one thing: if the mobile terminal needs to adapt to the screen, it has to rely on viewport to enable this ability.
The above is the detailed content of What is the viewport meta tag in HTML for?. For more information, please follow other related articles on the PHP Chinese website!

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