In web design, CSS background images are a powerful tool for creating visually appealing layouts. However, when it comes to SEO, they can be a double-edged sword. Unlike standard HTML images (using the `<img>` tag), background images are often invisible to search engine crawlers. This means that if your important visual content is locked away in your CSS, you could be missing out on valuable opportunities for image search traffic and contextual signals for your page’s topic.

Think of your website as a museum. The paintings on the walls are your HTML images—they have labels (alt text) and are a key part of the exhibit. The color of the walls is your background image—it sets the mood but isn’t the main attraction. This guide will help you understand when to use background images and how to ensure your important visual content is always visible to search engines. For a complete overview of image optimization, see our guide to all images.

An illustration of an invisible image, symbolizing the importance of fixing background images.

When to Use Background Images (and When Not To)

The key to using background images effectively is to understand their purpose. Here’s a simple rule of thumb:

  • Use background images for decoration: If an image is purely for aesthetic purposes (e.g., a subtle pattern, a gradient, or an abstract design), a CSS background image is the perfect choice. These images don’t add to the content of the page and don’t need to be indexed.
  • Use `<img>` tags for content: If an image is a crucial part of your content (e.g., a product photo, a diagram, or an infographic), it should always be an HTML `<img>` tag. This allows you to provide descriptive alt text, which is essential for both SEO and accessibility.

The SEO and Accessibility Blind Spot

The main drawback of CSS background images is that they are not part of the Document Object Model (DOM) in the same way that `<img>` tags are. This has two major consequences:

  1. SEO: Search engines like Google have gotten better at rendering pages, but they still primarily focus on the HTML content. An image that is only referenced in a CSS file is much less likely to be crawled, indexed, and ranked in image search.
  2. Accessibility: Screen readers cannot “see” CSS background images, and there is no way to provide alt text for them. This makes them completely inaccessible to visually impaired users. For more on this, see our guide to missing alt text.

For a deeper dive into the technical side of image SEO, check out this guide from Semrush.

An illustration of a checklist, symbolizing the importance of making sure your website is free of background images.

Frequently Asked Questions

Are CSS background images bad for SEO?

Not necessarily, but they should be used for decorative purposes only. If an image is important for understanding the content of your page, it should be an HTML `<img>` tag with descriptive alt text, not a CSS background image.

Do search engines index CSS background images?

Generally, no. Search engines prioritize the content in the HTML of a page, and CSS background images are often ignored. If you want an image to be indexed and appear in image search results, it must be an `<img>` tag.

How can I make my background images more accessible?

Since CSS background images don’t have alt text, they are invisible to screen readers. If the image is purely decorative, this is acceptable. If it conveys information, you should use an `<img>` tag instead. Also, ensure that any text placed over a background image has sufficient color contrast to be legible.

Ready to make your images visible? Start your Creeper audit today and see how you can improve your website’s images.