Alt Tag (Alt Text)

An alt tag — more precisely the 'alt' attribute, providing alt text (alternative text) — is the text that describes the content and meaning of an image in HTML. It serves several purposes: it's read aloud by screen readers to convey the image to visually-impaired users (the primary accessibility purpose), it's displayed in place of the image if the image fails to load, and it's read by search engines to understand what the image depicts (image SEO). Alt text is a small but important piece of HTML — a short, descriptive text describing the image — that makes images accessible to people who can't see them and understandable to machines that can't 'see' them either.

Alt text matters to marketers for two main reasons: accessibility and SEO. Accessibility: screen readers rely on alt text to convey images to visually-impaired users, so descriptive alt text is essential for making web content accessible (and is a requirement under accessibility standards and laws). Without alt text, images are meaningless or invisible to these users. SEO: search engines use alt text to understand what images depict, which supports image search ranking and contributes to a page's overall content understanding — so descriptive, relevant alt text helps images (and pages) be found in search. Alt text thus serves both the ethical and legal imperative of accessibility and the marketing goal of discoverability, in one small attribute.

On accessibility, alt text is essential and often legally required. Visually-impaired users navigating with screen readers depend on alt text to understand images — an image without alt text is announced as just 'image' or skipped, conveying nothing, while good alt text describes the image's content and meaning so these users get the information. Accessibility standards (like WCAG) and laws (like the ADA in the US and equivalents) require alt text on meaningful images, making it a compliance necessity as well as an ethical one. Accessible content also reaches a broader audience and reflects well on the brand. Alt text is a basic, important element of web accessibility.

On SEO, alt text helps search engines understand and rank images and contributes to page content understanding. Search engines can't fully 'see' images, so they rely on alt text (and surrounding context) to understand what an image depicts — descriptive, relevant alt text supports image search visibility (images appearing in image search results) and contributes to the page's overall topical understanding. Good alt text is descriptive and relevant (genuinely describing the image), not keyword-stuffed (cramming keywords into alt text is a misuse that doesn't help and can be seen as manipulative). So alt text serves SEO when it genuinely and concisely describes images. The two purposes — accessibility and SEO — align: good alt text that genuinely describes images serves both, which is why writing proper alt text is a basic best practice for both accessibility and image SEO.

Writing alt text well means providing concise, descriptive, genuine descriptions of meaningful images that convey their content and purpose — serving both screen-reader users (who need to understand the image) and search engines (which need to understand what it depicts). It means describing images accurately and helpfully (what the image shows and means in context), keeping descriptions concise, handling decorative images appropriately (decorative images can have empty alt text so screen readers skip them), and avoiding keyword-stuffing (which serves neither accessibility nor genuine SEO). Good alt text is a small effort that delivers both accessibility compliance and image-SEO benefit.

The failures are missing alt text on meaningful images (failing accessibility and image SEO), unhelpful or inaccurate alt text (that doesn't genuinely describe the image), keyword-stuffed alt text (misuse that doesn't help SEO and ignores accessibility), and treating alt text as an SEO-only or skippable detail. The discipline is to write concise, descriptive, genuine alt text for meaningful images — serving accessibility (the primary purpose) and image SEO together — recognizing alt text as a small but important element that makes images accessible to those who can't see them and understandable to machines, fulfilling both an accessibility requirement and a discoverability opportunity.

An alt tag (alt text) — describing an image for screen readers and search engines — serves accessibility and image SEO together, a small but important attribute that makes images accessible and findable.

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