Images are a key part of web design and user engagement, but without proper context, they can become invisible to search engines and inaccessible to users relying on assistive technologies. Alt tags solve this by giving images meaning and purpose within your content. They support accessibility, improve SEO, and ensure your visuals contribute to your site’s overall performance.

What Is an Alt Tag?

An alt tag—also called alt attribute or alternative text—is an HTML attribute applied to image tags (<img>) that describes the image’s content. The text within this attribute is displayed if the image fails to load and is also read aloud by screen readers for visually impaired users.

While users may not always see alt text directly, search engines rely on it to interpret what the image is about, making it a vital element for accessibility and search visibility.

Why Image Alt Tags Matter for SEO

Alt tags contribute to search engine optimization by providing descriptive information that enhances how search engines index images and understand the surrounding content. Their impact includes:

  • Image SEO: Well-written alt text increases the likelihood that your images appear in image search results.
  • Relevance Signals: They help clarify the context of a page and support overall keyword relevance.
  • Accessibility Compliance: Alt tags ensure your site meets accessibility standards, which is increasingly important for legal and ethical reasons.
  • Fallback Support: If images fail to load, alt text provides a textual description in its place, maintaining usability.

Best Practices for Writing Alt Tags

Here are our best practices for writing image alt tags:

  • Be Descriptive and Specific: Describe what the image shows, especially if it conveys important content.
  • Keep It Concise: Aim for short, clear descriptions—usually under 125 characters.
  • Use Keywords Thoughtfully: Include relevant keywords if appropriate, but avoid stuffing or over-optimization.
  • Don’t Use Phrases Such As “Image of” or “Picture of”: Screen readers already identify the element as an image, so such phrases are unnecessary.
  • Avoid Empty or Generic Text: Phrases like “photo1.jpg” or “graphic” add no value.

When to Leave Alt Tags Empty

There are cases where leaving an alt tag empty is acceptable and even recommended. For purely decorative images—such as background flourishes or spacing elements—an empty alt tag (alt=””) tells screen readers to skip them. This reduces noise and improves the browsing experience for visually impaired users.

However, avoid omitting the alt attribute entirely, as doing so may cause screen readers to read out the file name or other irrelevant code.

Common Mistakes to Avoid

Here are some common mistakes to avoid when dealing with image alt tags:

  • Keyword stuffing alt text in an attempt to manipulate rankings. Unnatural overuse of keywords is always a bad idea in any type of content- and image alt tags are no exception to this rule.
  • Using the same alt text across multiple images, which reduces relevance.
  • Ignoring alt tags altogether, leaving images invisible to search engines and screen readers.
  • Describing visual elements that don’t need description, like layout icons or decorative borders.