Optimizing Image Alt Text for Improved SEO

Introduction

Image alt text (the alt attribute) is a short written description used when an image can’t be seen. It matters for accessibility because screen readers announce it, and it matters for SEO because search engines use it to understand what an image shows and how it relates to the page (including image search visibility).^[1]

Most sites miss in two ways: informative images ship with blank alt, or every image gets a keyword dump. The better rule is consistent: describe what’s actually there, then add a keyword only when it naturally fits.

Below is a repeatable 5-step process you can use on any page, plus the edge-case rules that prevent the most common template mistakes.

What Alt Text Does (and When You Should Use It)

Alt text is read by screen readers and used when images fail to load. For SEO, it’s a relevance signal that helps search engines interpret the image and the surrounding page topic—strongest when the nearby copy matches the same intent.^[1]

Not every image needs descriptive alt. Use empty alt (alt="") for purely decorative images—flourishes that add no information and shouldn’t interrupt reading. Empty alt tells assistive tech to skip the image instead of announcing repeated noise.

Quick distinctions:

• Alt text: what the image means for someone who can’t see it.
• Caption: visible text for everyone; can be longer and more explanatory.
• Filename: a file identifier; useful housekeeping, not a replacement for alt.

Examples

• Decorative squiggle under a headline → alt=""
• Photo that supports a “how to” step → describe what’s needed to complete the step

Alt Text Playbook: The 5-Step Writing Formula

Use this workflow to write or audit alt text. When I ran content audits across large blogs, this sequence cut down both “blank” misses and keyword stuffing, and it made reviews faster.

Step 1: Identify the image’s purpose

• Informative (adds meaning): needs descriptive alt.
• Decorative (style only): use alt="".
• Functional (button/link): alt should describe the action.

Step 2: Describe what’s essential

Include only what a user needs:

• Who/what is shown
• Action (if any)
• Context that matters to the page

Step 3: Keep it concise and specific

Aim for a short phrase or one sentence. Cut filler (“beautiful,” “high-quality”) and anything that doesn’t change understanding.

Step 4: Add a keyword only if it fits naturally

Include a keyword only when the topic is visible and relevant. Don’t use alt text to target something the image doesn’t show.

Step 5: Remove redundancy

Skip “image of…” (screen readers already announce it). Avoid repeating nearby text word-for-word (captions, headings, adjacent sentences).

If the image contains text users need (like a settings screenshot), include only the meaningful text—not every UI label or decorative element.^[2]

Keyword and Relevance Best Practices (Without Stuffing)

Alt text supports SEO when it aligns with the page topic and the actual image content.

• Match page intent. “Team working in an office” is vague; “Editor adding alt text in a WordPress media library” fits an alt-text guide.
• Don’t stack keywords. One image is not a place for “alt text SEO, image SEO, optimize images, alt tags.” It reads poorly and adds risk with little upside.
• Avoid lists and awkward phrasing. If it sounds wrong read aloud, it’s wrong for screen readers and usually wrong for SEO.
• Use specifics only when they’re visible and helpful. Product names, model numbers, and brand terms belong in alt when they’re shown and matter (e.g., “Asics Gel-Kayano 30 running shoe, side view”).
• Support, don’t duplicate. If the paragraph already states the takeaway, alt should add what’s unique in the image rather than restating the same sentence.

Sometimes the best SEO choice is leaving a target keyword out—if it isn’t visible, accuracy wins.

Compact examples (Bad → Better)

• Informative photo: alt="man at computer" → alt="Content editor writing alt text for product images in Shopify"
• Product image: alt="best running shoes cheap running shoes" → alt="Asics Gel-Kayano 30 running shoe, side view in black"
• Decorative image: alt="blue wave design" → alt=""
• Functional icon/button: alt="magnifying glass icon" → alt="Search"
• Chart/infographic: alt="SEO traffic chart" → alt="Line chart showing organic sessions rising from January to June" (add a longer description nearby)

Edge Cases: Decorative Images, Logos, Icons, and Linked Images

Most real-world failures happen in templates, where the same pattern repeats across hundreds of pages.

• Decorative/background flourishes: Use alt="" and keep them out of reading order when possible (CSS backgrounds are often better for purely decorative visuals).
• Logos: Use the brand name (e.g., alt="Seosoft"). Add a tagline only if it adds meaning not present elsewhere.
• Icons/buttons (functional images): Describe the action: alt="Download PDF", alt="Play", alt="Close". For true UI controls, an aria-label may be appropriate; keep the label/action consistent either way.^[2]
• Linked images: Describe the destination or action. A banner to pricing should be alt="View pricing" (or “Pricing page”), not “blue banner with circles.”
• Charts/infographics: Put the key takeaway in alt, then provide the full explanation in nearby text (or a longer description) so users can access the data and conclusion.

Sources

1. Google Search Central: Image SEO best practices
2. W3C WAI: An alt Decision Tree