References

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The HTML imagesizes attribute

Attribute All modern browsers Updated
Quick answer

The HTML imagesizes attribute provides the sizes hint for a preloaded responsive image, mirroring an <img> sizes. It is used on the <link rel="preload" as="image"> element.

Overview

The imagesizes attribute sets the sizes hint for a preloaded image. It is used on document head elements like <meta>, <link> and <script>.

It belongs to the document head — metadata, stylesheet and script loading, encoding and resource hints. These attributes shape how the page is interpreted and how efficiently its resources load.

Syntax

<link rel="preload" as="image" imagesrcset="s.jpg 480w, l.jpg 1080w" imagesizes="(max-width:600px) 480px, 1080px">

Values

Value
A sizes string — media-condition / length pairs.

Best practices

  • Declare the character encoding with <meta charset="utf-8"> first in the <head>.
  • Load scripts with defer (or as modules) so they do not block parsing.
  • Protect third-party resources with integrity and crossorigin (Subresource Integrity).
  • Use resource hints like preload deliberately, paired with the right as value.

Frequently asked questions

What does the imagesizes attribute do?
Sets the sizes hint for a preloaded image.
Where do head attributes apply?
On the metadata elements in the <head> — <meta>, <link>, <script> and <base>.
What is the difference between async and defer?
async runs a script as soon as it loads in no set order; defer runs scripts in order after the document is parsed.
Which elements use the imagesizes attribute?
It is an element-specific attribute, used on document head elements like <meta>, <link> and <script>.
http-equiv imagesrcset