What is Image Alt Text?

Image alt text: describing what eyes might miss

Image alt text is the words you choose to represent an image when the image itself cannot be perceived—slow connections, screen readers, or search systems parsing non-visual signals. It answers: “What is this image communicating?”

This is a content and UX concept. The alt attribute is how that text is encoded in HTML. Strong on-page SEO treats alt text as part of primary content messaging—not a keyword dump in a hidden field.

Image alt text vs related concepts

Alt text should not duplicate captions word-for-word unless both truly need the same string—often captions add commentary alt should not repeat.

When images need alt text

Informative images

Charts, product photos, screenshots illustrating UI steps—the alt text states the insight: “Line chart showing crawl requests doubling after sitemap fix.”

Functional images

Icons inside buttons: alt describes action—“Search,” “Add to cart”—not “magnifying glass icon.”

Linked images

Alt text names the link purpose: “Download crawl budget PDF” when the image is the only link content.

Decorative images

Hero backgrounds, spacers, ornamental flourishes—use empty alt so assistive tech skips them. Do not stuff keywords into decorative slots.

Writing good image alt text

1. Convey the same function as the image — not “image of” unless format matters.
2. Include critical text shown in the image — if the image is mostly text, alt should carry it.
3. Stay specific to page context — “2026 core update timeline” beats “timeline.”
4. Avoid keyword lists — write for humans first.
5. Match language of the page — localized alt for localized URLs.
6. Do not use filename as alt — IMG_4521.jpg helps nobody.

Example: product photo

Alt: “Crawlox dashboard showing internal link report with orphan URLs highlighted.” Supports image search and clarifies primary content about reporting features.

Example: decorative stock photo

Smiling handshake photo adds no information—alt="" correct. Stuffing “SEO services handshake” is spammy alt text.

Image alt text and on-page SEO

Google Images uses page topic, alt text, captions, structured data, and file signals together. Alt text alone cannot rank a irrelevant page, but missing alt on key diagrams wastes clarity in Google Images and accessibility audits.

Place informative images near relevant paragraphs and introduction sections so surrounding copy reinforces the same entities alt text names.

Image alt text vs anchor text

When an image is the sole content of an internal link or external link, alt text functions like anchor text for accessibility APIs. Write alt as link label: destination or action, not visual description alone if misleading.

Example: logo linking home → alt “Crawlox home” not “logo.”

Common image alt text mistakes

Image alt text in CMS workflows

Train authors to fill alt in upload dialogs—not post-hoc bulk filename rewrites. Templates should require alt for hero and product slots; block publish if informative image lacks description.

Automated “AI alt” generation needs human review for accuracy on technical screenshots.

Image alt text for complex media

Charts: Summarize trend in alt; put data table nearby for full detail. Infographics: Short alt plus long caption or article body expansion. Code screenshots: Alt states what code demonstrates.

Do not put entire articles inside alt—use page paragraphs for depth.

Image alt text myths

• Myth: “Alt text is only for accessibility—not SEO.” Both benefit from the same clear descriptions.
• Myth: “Repeat primary keyword in every image alt.” One natural use beats ten forced repeats.
• Myth: “Google reads CSS background images’ alt.” Backgrounds need different techniques; alt applies to img elements.

How Crawlox audits image alt text

Crawlox lists images per URL—missing alt, empty alt on informative templates, suspiciously identical alt across thousands of URLs, and alt that mirrors image filename patterns without semantic value. Fix alt text at the content layer; verify the alt attribute is present in deployed HTML after CMS publish—not only in the database field.

Image alt text in content governance

Publish checklists should block release when hero or inline diagrams lack alt text review. Store alt strings in CMS with version history so regressions after template changes are traceable. Pair alt governance with image caption rules—authors know which field answers “what is it?” versus “why does it matter?”

Image alt text and decorative classification

Design systems should tag image slots as informative vs decorative at component level—automatic alt="" for decorative heroes, required alt for product and chart slots. Classification prevents authors from keyword-stuffing decorative banners because the CMS always demands a text field.

Image alt text review rubric

Score alt drafts on accuracy, brevity, and context fit—not keyword count. A three-point rubric in editorial QA: (1) would a colleague understand the image without seeing it, (2) does alt avoid redundant image caption copy, (3) does alt avoid banned patterns like “image of” plus filename tokens from image filename paths.

Image alt text for icons and UI affordances

Interface screenshots in docs need alt describing the control state—“Save button disabled until form valid”—not generic “screenshot.” UI image alt text should match what a tester would verify in QA, especially when images document steps in primary content procedures.

Image alt text localization workflow

Localized pages need translated alt—not English alt on German articles. Workflow: translate alt in TMS alongside body paragraphs; verify alt attribute in localized template output, not only in the default locale preview.

Image alt text for SVG and inline graphics

Inline SVG icons need title or aria-label patterns—not always img alt—but the same content principles apply: describe function for informative icons, hide decorative vectors from assistive APIs. Document which component pattern your design system uses so SEO audits do not only check img tags.