Image alt text, the off-page anchor surface Google reads alongside text anchors.
When an inbound link wraps an image, Google uses the alt attribute as the anchor text. Image anchors count in the per-URL anchor distribution Penguin 4.0 evaluates. The discipline that runs across descriptive alt-text on the link-target page (for accessibility, for Google Images traffic, for editorial-link quality) and the alt-attribute spec on outreach image embeds (for per-URL exact-match concentration) is one surface.
Four reads on the image-anchor surface and the accessibility-SEO alignment.
Alt text serves two audiences (screen readers and search engines) on the same attribute. The off-page implication is image anchors count in the per-URL Penguin evaluation; the on-page implication is link-target alt-text discipline shapes link-pass-through quality and compounds Google Images traffic into branded query volume.
Google reads the alt attribute as the anchor text on image-wrapped links.
When an HTML link element wraps an image rather than text, Google uses the image's alt attribute as the anchor text for that link. The implication for off-page SEO: image-embed placements that link to a landing page contribute to the per-URL anchor distribution Penguin 4.0 evaluates. An exact-match alt attribute on an inbound image embed counts toward the per-URL exact-match concentration, the same way a text-wrapped exact-match anchor would. Image anchors do not get a separate accounting bucket from the Penguin evaluation surface; they sit alongside text anchors in the per-URL profile.
Good alt text descriptive examples versus thin examples.
Descriptive alt text names what the image shows in plain language. Thin alt text repeats the file name, leaves the attribute empty when the image carries information, or stuffs the attribute with commercial-intent queries unrelated to the image. Descriptive examples: alt="Anchor-text distribution chart showing 70 percent branded and 5-15 percent exact-match against per-vertical baseline" on a methodology diagram; alt="Featured.com query digest interface with topic filters and deadline column" on a platform screenshot. Thin examples that fail both accessibility and SEO: alt="image-37.png", alt="" on an information-carrying image, alt="off-page SEO agency link building services backlinks" stuffed with queries unrelated to the image.
Accessibility requirements under WCAG 2.1 Level A.
The Web Content Accessibility Guidelines (WCAG) 2.1 Success Criterion 1.1.1 (Non-text Content) requires every image that carries information to have a text alternative. Decorative images that carry no information use alt="" (empty attribute, not missing attribute) so screen readers skip them. Functional images (icons inside buttons, image-wrapped links) use alt text describing the function rather than the image. The WCAG 2.1 Level A rule applies to every public site; the accessibility surface and the SEO surface align because the alt attribute serves both audiences (screen readers and search engines). An off-page link target page with proper alt-text discipline reads as a peer-quality publication; a target page with missing or stuffed alt attributes reads as low-quality and degrades the publisher reputation that drives inbound editorial linking.
Schema interaction: ImageObject with caption and contentLocation.
Schema.org's ImageObject type provides structured-data fields adjacent to the alt attribute. The caption field provides a visible image caption; the contentLocation field provides the geographic context where the image was captured; the creator field names the photographer or designer; the license field declares the usage rights. ImageObject markup nested inside an Article schema or a Product schema feeds Google Images with structured context beyond the alt attribute. The off-page implication: link-target pages that ship proper ImageObject markup alongside descriptive alt text accumulate Google Images traffic in parallel with the editorial-link signal, which compounds branded query volume the brand-strength signal reads.
Methodology questions we get during the audit conversation.
Does image alt text affect off-page SEO?
Image alt text matters in off-page SEO when an inbound link wraps an image rather than text. Google reads the image's alt attribute as the anchor text for that link, and the alt-attribute anchor counts in the per-URL anchor distribution Penguin 4.0 evaluates against the per-vertical baseline. An exact-match alt attribute on an inbound image embed counts toward the per-URL exact-match concentration alongside text-wrapped anchors. Beyond the inbound-link surface, the alt-text discipline on the link-target page itself affects link-pass-through quality: a target page with proper alt-text discipline reads as peer-quality publication to editorial linkers, and the Google Images traffic the alt attributes generate compounds branded query volume that the brand-strength signal reads.
What does good image alt text look like?
Descriptive alt text names what the image shows in plain language, in 8 to 15 words for content-bearing images. Working examples: alt="Anchor-text distribution chart showing 70 percent branded and 5-15 percent exact-match against per-vertical baseline" on a methodology diagram; alt="Featured.com query digest interface with topic filters and deadline column" on a platform screenshot; alt="Penguin 4.0 timeline showing September 2016 core-algorithm integration" on a date-anchored visual. Thin patterns to avoid: alt="image-37.png" repeating the filename; alt="" on an information-carrying image; alt="off-page SEO agency link building backlinks" stuffed with commercial queries unrelated to the image content.
When should an image have an empty alt attribute?
Decorative images that carry no information use alt="" (empty attribute, not missing attribute). Screen readers announce the alt text for non-empty attributes and skip empty attributes entirely; a missing alt attribute on an image element causes screen readers to announce the filename or the word "image," which degrades the assistive-tech experience. WCAG 2.1 Success Criterion 1.1.1 (Non-text Content) treats alt="" as the correct attribute for purely decorative images (background flourishes, pure-aesthetic dividers, hairline rules). Functional images (icons inside buttons, image-wrapped links) use alt text describing the function rather than the image content.
What is the ImageObject schema and how does it interact with alt text?
Schema.org's ImageObject type provides structured-data fields adjacent to the alt attribute. The caption field provides a visible image caption; the contentLocation field provides geographic context for the image; the creator field names the photographer or designer; the license field declares usage rights. ImageObject markup nested inside Article or Product schema feeds Google Images with structured context beyond the alt attribute. Pages that ship proper ImageObject markup alongside descriptive alt text accumulate Google Images traffic in parallel with the editorial-link signal, which compounds branded query volume.
How does image alt text fit into a broader off-page campaign?
Image alt text is one slice of the per-URL anchor-distribution surface. The off-page SEO services mix scopes alt-attribute copy on inbound image embeds with the same anchor-allocation discipline as the text-anchor surface, the same per-vertical exact-match ceiling (5 to 15 percent), and the same per-URL Penguin 4.0 evaluation. Outreach campaigns that include image embeds (infographic placements, methodology diagrams, data visualizations) brief the alt attribute as part of the placement spec, the same way they brief the text anchor. A campaign that ships clean text-anchor allocation but stuffed image alt attributes still exposes the per-URL profile to Penguin discounting.
The audit reads alt-text exposure on inbound image embeds against the per-URL anchor profile.
The audit pulls the inbound profile (including image-wrapped links), surfaces alt-attribute exact-match concentration per URL, and names the placement specs where alt-text copy briefs the campaign target.