The core of the implementation of responsive images is to use HTML's srcset and sizes attributes to match CSS styles. 1. Use srcset to specify multiple pictures of different sizes and mark their widths (such as 480w, 800w, 1200w), so that the browser can automatically select the most suitable picture according to the viewport width; 2. Use sizes to define the display ratio of the picture under different screen sizes, such as "(max-width: 600px) 100vw" to indicate that the viewport is full of the small screen, otherwise it will account for half the width; 3. Set img { max-width: 100%; height: auto; } in CSS to ensure that the picture is adapted to the container and maintain the proportion; 4. Optionally, use x units (such as 1x, 2x) in srcset to adapt to a high-resolution screen to improve the display effect of the Retina screen. These methods jointly ensure the clarity and adaptability of the pictures on various devices.
Responsive images are very important in modern web design, especially today when device screen sizes are becoming increasingly different. Simply put, using srcset
and sizes
attributes to match CSS's max-width
or width: 100%
is the core method to implement responsive images .
Here are some practical suggestions:
Specify multiple images using srcset
The browser needs to select the most suitable picture based on the device's resolution, pixel density and screen width. srcset
is used to tell the browser what are the optional pictures.
<img src="/static/imghw/default1.png" data-src="small.jpg" class="lazy" srcset="small.jpg 480w, medium.jpg 800w, large.jpg 1200w" alt="Example Picture" />
-
480w
,800w
,1200w
represent the width of the picture (units in pixels). - The browser will automatically select the most suitable picture based on the current viewport width.
Tell the browser how to display it with sizes
It is not enough to have srcset
alone, because images may occupy different width ratios under different layouts. At this time, sizes
attribute needs to be used.
<img src="/static/imghw/default1.png" data-src="small.jpg" class="lazy" srcset="small.jpg 480w, medium.jpg 800w, large.jpg 1200w" sizes="(max-width: 600px) 100vw, 50vw" alt="responsive picture" />
Explain sizes
above:
- When the screen width is less than or equal to 600px, the picture covers the entire viewport width (100vw);
- Otherwise, it will account for half of the viewport width (50vw).
This way the browser can more accurately decide which image to load.
Setting basic styles in CSS
In order to make the picture scale freely on different devices, some basic styles are usually required in CSS:
img { max-width: 100%; height: auto; }
-
max-width: 100%
ensures that the image does not exceed the container; -
height: auto
keeps the image proportions unchanged.
These two properties are suitable for almost all responsive image scenarios and are "standard".
Additional tips: High resolution adaptation (Retina)
If you want to display a clearer picture on the Retina screen, you can use x
units to represent pixel density in srcset
:
<img src="/static/imghw/default1.png" data-src="standard.jpg" class="lazy" srcset="standard.jpg 1x, high-res.jpg 2x" alt="HD adapter picture" />
-
1x
is the standard resolution; -
2x
is twice the pixel density, suitable for high-definition screens.
In general, the key to responsive images is HTML srcset
and sizes
, plus a little simple CSS control. Although it may seem a bit complicated, you can easily deal with most scenarios by understanding the role of each attribute.
Basically that's it.
The above is the detailed content of How to create responsive images in CSS?. For more information, please follow other related articles on the PHP Chinese website!

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