How to set web page background image with CSS and optimize loading? First, select the appropriate background image, select JPG/WebP/PNG format according to the purpose, and pay attention to copyright in a unified style; second, use CSS attributes to set the background image, including background-image specified path, background-repeat control duplication, background-size and background-position adaptation to the screen; third, optimize the loading speed, improve the user experience by compressing images, using WebP format, delaying loading, adding transition effects and setting transition colors.

In web design, background images are an important element to enhance visual appeal. But if you want to use it well, adding a picture is not enough. You have to match the reasonable settings of the CSS attributes to make the page look good and stable.

How to choose the right background image?

The higher the picture selection, the better, the better. It should be judged based on the purpose. If it is a decorative large image background, you can choose a compressed JPG or WebP format; if small icons or patterns with transparent background are needed, PNG is more suitable. In addition, the picture style should also be consistent with the overall website to avoid visual confusion.

You should also pay attention to copyright issues, and don’t just download pictures from the Internet and use them directly. You can use resources from free photo galleries such as Unsplash and Pixabay, or create original content yourself.

What are the commonly used CSS properties for setting background images?

background-image is the most basic property, used to specify the image path:

 background-image: url('bg.jpg');

If you also want the background not to be covered with repeated repetitions, add background-repeat: no-repeat; . This way the picture is displayed only once, which is suitable for the background of the homepage large picture.

In order to ensure that the pictures are adapted to different screen sizes, it is recommended to add:

• background-size: cover; (image is scaled in a uniform ratio, covering the entire container)
• background-position: center; (center alignment)

These combined can make the background image perform well on various devices.

How to optimize loading speed and user experience?

A large background image is a common problem, slow loading is a There are several ways to alleviate this problem:

• Image compression: Use tools such as TinyPNG and ImageOptim to reduce file size.
• Using modern formats: WebP has higher compression rates and is not bad in quality than JPEG and PNG.
• Lazy loading: For background images that are not on the first screen, lazy loading technology can be used to wait for the user to scroll to the corresponding area before loading.
• Add a fade effect: It will be a bit abrupt when the image suddenly appears when loading. You can use CSS to transition to make it appear slowly.

You can also consider setting a transition color for areas that have not been loaded, such as:

 background-color: #f5f5f5;

This way, even if the picture has not been loaded, the page will not look like it will not look space.

Basically that's it. The key to making good use of background images is to balance beauty and performance, and don’t blindly pursue high picture quality and ignore the loading experience.

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