TL;DR

Alt text describes images to search engines and screen readers. Google can't 'see' images — only read alt text — so without it, images are invisible for SEO. Write descriptive, natural alt text; don't stuff keywords.

Key Points

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Google explicitly states that alt text is used to understand image content for Google Images ranking and for accessibility

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Decorative images (dividers, icons, backgrounds) should use empty alt text (alt='') — this tells screen readers to skip the image

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Alt text should describe what the image shows, not repeat the surrounding text or keyword-stuff

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Missing alt text on important images (product photos, instructional diagrams) leaves significant SEO value uncaptured

Writing Effective Alt Text

Good alt text is specific, concise, and descriptive of what the image actually shows^[1]. For a photo of a person making espresso: 'barista tamping espresso grounds into portafilter' is better than 'coffee' (too vague) or 'best espresso machine coffee brewing tutorial step 3' (keyword-stuffed). Include the target keyword naturally if it's relevant to what the image shows — if you have an image of a keyword research spreadsheet on a keyword research page, 'keyword research spreadsheet with search volume and difficulty columns' naturally includes the keyword while being accurate. Keep alt text under 125 characters — screen readers typically announce this attribute and excessively long alt text interrupts the reading flow. Use empty alt text (alt='') for purely decorative images so screen readers skip them rather than reading out meaningless descriptions.

Alt Text and Google Images

Google Images is a significant traffic source that many sites overlook^[1]^[2]. Optimized images with accurate alt text can drive substantial referral traffic from image searches — particularly for visual industries (design, food, fashion, real estate, products). Google uses alt text as the primary signal for understanding what an image depicts, alongside the surrounding text, the image filename, and the page's overall topic. Including relevant keywords in alt text (naturally, not stuffed) can help images rank in image search for those terms. Use descriptive filenames too — 'espresso-machine-portafilter.jpg' is better than 'img0042.jpg.' For product-based businesses, properly alt-texted product images appear in Google Shopping surfaces, generating additional discovery touchpoints beyond standard text search.

Alt Text for Accessibility and SEO Combined

Alt text serves dual masters: search engines and users with visual impairments^[2]. For SEO, the goal is keyword-relevant descriptions that help Google understand image content. For accessibility, the goal is describing the image accurately enough that a blind user understands what they're missing. These goals align in most cases: a descriptive, specific alt text serves both. Screen readers announce alt text to visually impaired users navigating with assistive technology — poor alt text ('image1', 'photo', 'click here') creates a confusing experience. The E-E-A-T connection is real: websites that implement proper alt text demonstrate care for all users, which Google's quality raters evaluate. WCAG (Web Content Accessibility Guidelines) 2.1 specifies that all informative images must have text alternatives — accessibility compliance and SEO optimization are aligned, not competing priorities.

SOURCES

Google Search Central — Use Descriptive Alt Text for Images

Moz — Alt Text for SEO: How to Optimize Your Images

Last updated: June 9, 2026

Related Terms

Schema Markup

Structured data code added to a web page's HTML that helps search engines understand content context and enables rich results like star ratings, FAQs, breadcrumbs, and event details in the SERP.

Page Speed

The amount of time it takes for a web page to load and become usable for a visitor — a direct Google ranking factor measured by Core Web Vitals metrics including Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift.

E-E-A-T

Experience, Expertise, Authoritativeness, and Trustworthiness — Google's framework for evaluating content quality, used by human Quality Raters to assess search result quality and inform algorithm development.

Open Graph

A protocol developed by Facebook that uses `<meta>` tags in a page's `<head>` to control how content appears when shared on social media platforms — defining the title, description, image, and URL shown in link previews.

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