Definition: Alt text (alternative text) is a brief written description added to the alt attribute of an HTML image element. For example, an image element may use src="example.jpg" alt="Descriptive text here" to identify the image file and describe its content or function. It serves two parallel purposes: it communicates image content to search engines, which cannot directly interpret images, and it is read aloud by screen readers for users who are visually impaired or browsing with images disabled.
Why It Matters: Alt text is one of the few elements that sits at the intersection of SEO and accessibility, making it doubly important. For SEO, descriptive alt text helps Google understand what images depict, improves image search visibility, and contributes to the overall relevance signals of a page. For accessibility, missing or inadequate alt text creates a significant barrier for screen reader users – a WCAG compliance concern that can also affect compliance with the ADA and Section 508. Well-written alt text that accurately describes images and naturally includes relevant keywords improves both ranking potential and inclusiveness.
How It Works: Alt text is added to an HTML image element using the alt attribute. A simplified example is src="example.jpg" alt="Descriptive text here". In WordPress, the Alt Text field appears in the Media Library and block editor for every image. Best practices include describing what is visually shown in the image concisely, naturally incorporating the page’s target keyword where contextually relevant, using an empty alt attribute for purely decorative images, and avoiding generic phrases such as “image of” or “photo of.” SEO audit tools such as Screaming Frog and Semrush can identify pages with missing alt text.
Related: On-Page SEO, Accessibility, WCAG, Image Search, Structured Data