Alt Text

Alt text (alternative text) is an HTML attribute added to image tags that provides a written description of the image’s content, serving as a text substitute for screen readers used by visually impaired users and helping search engines understand and index image content.

What Alt Text Means in Practice

Alt text operates at the intersection of web accessibility and SEO. It’s a single attribute in an image tag (<img alt="description here">) that does two jobs: it tells assistive technologies what an image shows so that visually impaired users can understand the content, and it tells search engines what the image depicts so they can index it for image search and use it as a relevance signal for the page.

The accessibility function is the original and most important purpose. Screen readers, the software used by people who are blind or have low vision, read alt text aloud when they encounter an image. Without alt text, the screen reader either skips the image entirely or reads the file name, which is typically useless (“IMG_4372.jpg” tells the user nothing). For the estimated 2.2 billion people worldwide with vision impairment (World Health Organization data), alt text is the only way to access image content on the web.

The SEO function has grown in importance as Google has improved its image search capabilities. Google cannot fully “see” images the way humans can. While Google’s computer vision has improved dramatically, alt text remains the most reliable signal for understanding image content. Pages with descriptive, relevant alt text on their images tend to appear more frequently in Google Image search results and can earn additional traffic from that channel. For ecommerce businesses, Google Image search drives meaningful product discovery traffic. For healthcare practices, image search visibility for procedure photos, facility images, and provider headshots supports brand presence across search surfaces.

In practice, most websites do alt text poorly. The most common failure is leaving alt text empty. A study by the WebAIM Million analyzed the accessibility of the top 1,000,000 home pages and consistently finds that missing alt text is one of the most prevalent accessibility errors on the web. The second most common failure is writing alt text that’s either too generic (“image,” “photo,” “picture”) or stuffed with keywords (“best-dentist-chicago-dental-implants-affordable-whitening”). Neither serves the user or the search engine.

Good alt text is descriptive, concise, and contextually relevant. It describes what the image shows in a way that makes sense within the surrounding content. For a photo of a dental practice’s lobby on a location page, good alt text might be: “Pinnacle Dermatology reception area with modern seating and natural lighting.” That description helps a screen reader user understand the image, helps Google understand what the photo shows, and provides a topical relevance signal for the page.

For multi-location businesses with hundreds of location pages, alt text becomes a scalable optimization opportunity. Each location page typically includes photos of the facility, providers, and team. Unique, descriptive alt text for each image across every location page creates hundreds of additional relevance signals and image search entry points. We’ve seen multi-location healthcare clients generate measurable traffic from Google Image search after implementing systematic alt text optimization across their location page photos.

The Web Content Accessibility Guidelines (WCAG) 2.1, which define the legal standard for web accessibility under the Americans with Disabilities Act, require that all non-decorative images have meaningful alt text. This isn’t just a best practice; it’s a legal requirement for many organizations. Healthcare organizations, government agencies, educational institutions, and businesses above certain thresholds face potential ADA compliance lawsuits for inaccessible websites. Alt text is one of the most straightforward accessibility improvements available.

Why Alt Text Matters for Your Marketing

Alt text matters because it opens two additional channels of visibility: image search and accessibility compliance. Both have direct business implications that go beyond traditional SEO metrics.

Google’s image search accounts for approximately 22% of all web searches, making it one of the largest search surfaces after standard web search. Pages with well-optimized images and descriptive alt text are eligible to appear in these searches, driving additional traffic that pages with missing or poor alt text simply don’t capture. For visually rich industries like healthcare (procedure photos, facility tours), beauty (before-and-after images), and ecommerce (product photography), image search traffic can represent a meaningful percentage of total organic visits.

The accessibility dimension carries increasing business weight. Web accessibility lawsuits have grown significantly in recent years, and alt text is consistently among the most cited accessibility failures. Beyond legal risk, accessible websites serve a broader audience. Organizations that invest in accessibility signal professionalism and inclusivity that resonates with patients, customers, and partners.

How Alt Text Works

Alt text is implemented as an attribute within the HTML <img> tag. The syntax is simple: <img src="image.jpg" alt="Description of the image">. Content management systems like WordPress provide alt text fields in the media library, making it possible to add alt text without editing HTML directly.

Writing effective alt text follows a few principles:

• Describe the image’s content, not its purpose. Write what the image shows, not why it’s there. “Doctor examining a patient’s skin condition” is descriptive. “This image shows our expertise” is not.
• Keep it concise. Screen readers announce alt text as a single block. Aim for one to two sentences, roughly 125 characters. Longer descriptions are better handled with caption text or ARIA descriptions.
• Include relevant keywords naturally. If the image is a photo of dental implants on a dental implants service page, it’s natural and helpful to include “dental implants” in the alt text. But the alt text should describe the actual image, not be a keyword string.
• Don’t start with “image of” or “photo of.” Screen readers already announce the element as an image. Starting with “image of” creates redundancy: the user hears “image: image of a dental office.”
• Use empty alt text for decorative images. Purely decorative elements (borders, spacers, design flourishes) should have empty alt attributes (alt=""), not missing alt attributes. Empty alt tells the screen reader to skip the image. Missing alt causes it to read the file name.

Alt text for different image types:

• Product photos: Describe the product with specifics. “Red Nike Air Max 90 running shoe, side profile view” is better than “shoe.”
• Staff/provider photos: Include the person’s name and role. “Dr. Sarah Chen, board-certified dermatologist at Pinnacle Dermatology” provides context.
• Charts and graphs: Describe the key finding. “Bar chart showing 40% increase in organic traffic over 6 months” communicates the data point.
• Screenshots: Describe what the screenshot shows. “Google Search Console dashboard showing indexing coverage report with 95% valid pages.”
• Hero/banner images: Describe the scene. “Aerial view of downtown Chicago skyline at sunset” for a Chicago office location page.

Common mistakes include leaving alt text blank (the most prevalent error), writing the same generic alt text for every image (“office photo,” “team photo”), stuffing keywords without describing the image, writing alt text that’s hundreds of words long, and forgetting to update alt text when images are replaced. Regular alt text audits using crawling tools like Screaming Frog flag missing and duplicate alt text across the site.

External Resources

• Google’s Image SEO Best Practices — Google’s official guidance on optimizing images for search, including alt text recommendations
• WebAIM’s Alternative Text Guide — The definitive accessibility guide to writing effective alt text, including decision trees for different image types
• W3C Web Content Accessibility Guidelines (WCAG) 2.1 — The official standard for non-text content accessibility, including alt text requirements
• Moz’s Guide to Image SEO — Practical SEO-focused guide to alt text implementation and image optimization

Related Resources

• The Technical SEO Audit Guide: A Practitioner’s Methodology — How image and alt text auditing fits within a comprehensive technical SEO review
• The Ultimate SEO Checklist: A Complete Guide for 2026 — Where alt text optimization fits within a complete on-page SEO framework
• SEO for Healthcare: What Multi-Location Practices Get Wrong — How healthcare practices can optimize provider and facility images across location pages
• A Beginner’s Guide to Shopify SEO — How alt text optimization applies to ecommerce product images for Shopify stores

Related Glossary Terms

• Title Tag: The HTML element that defines a page’s headline in search results. Like alt text, the title tag is an on-page HTML element that serves both users and search engines.
• Technical SEO: The practice of optimizing website infrastructure for search engines. Alt text implementation is one of the foundational on-page elements in technical SEO.
• Core Web Vitals: Google’s page experience metrics that include image loading performance. Properly sized and optimized images (with alt text) contribute to better Core Web Vitals scores.
• Indexing: The process by which search engines add content to their database. Alt text helps search engines index images, making them discoverable through Google Image search.