Alt text, short for alternative text, is a written description added to images in HTML using the alt attribute. Google’s official documentation at developers.google.com/search/docs/appearance/google-images#use-descriptive-alt-text provides the complete specification. The text serves two primary functions: it appears when images cannot load, and screen readers announce it to users who cannot see images. The code format is <img src=”image.jpg” alt=”Description of what the image shows”>.
Search engines cannot see images the way humans do. They rely on alt text to understand what images depict and how images relate to surrounding content. This understanding influences both image search rankings and the overall topical relevance signals for the page containing the image. Without alt text, images are invisible to search engines and inaccessible to users relying on assistive technology.
The dual purpose of alt text creates tension between accessibility requirements and SEO optimization. Accessibility standards demand descriptions that help blind users understand image content. SEO instincts push toward keyword inclusion. The best alt text accomplishes both by accurately describing images using natural language that happens to include relevant terms when those terms genuinely describe what appears in the image.
Nakamura, Accessibility Specialist Focus: Screen Reader Experience
Screen readers announce alt text when users navigate to images. The announcement provides the only information blind users receive about visual content. Poor alt text leaves users confused about what they missed. Missing alt text forces screen readers to announce file names, which typically sound like “image underscore 47382 dot jpg” and provide zero useful information.
Effective alt text describes what matters in the image for the context where it appears. A photo of a person signing a document needs different alt text on a legal services page versus a pen manufacturer’s product page. The legal page might use “Client signing estate planning documents with attorney present.” The pen page might use “Executive using Montblanc fountain pen to sign contract.” Same image, different relevant details.
Decorative images that add visual interest but no informational content should have empty alt attributes. The code reads alt=”” with nothing between the quotes. This tells screen readers to skip the image entirely rather than announcing it. Users do not need to hear “decorative swirl” or “blue gradient background” when those elements add nothing to their understanding.
Alt text length should match description needs. Simple images need short descriptions. Complex images like charts, infographics, or detailed diagrams may need longer descriptions or supplementary text on the page. Screen reader users cannot skim alt text the way sighted users skim images. Every word gets announced sequentially. Excessive length wastes their time.
Testing with actual screen readers reveals problems that code inspection misses. Listen to how your alt text sounds when announced. Awkward phrasing, excessive length, and missing context become obvious when you hear them rather than read them. NVDA and VoiceOver are free screen readers available for testing.
Lindstrom, Search Systems Researcher Focus: How Search Engines Process Images
Search engines use alt text as primary signal for understanding image content. When Googlebot encounters an image, it cannot interpret the visual information directly. It reads the alt attribute, the surrounding text, the file name, and the page context to determine what the image depicts and whether it should appear in image search results.
Alt text influences page-level topical signals beyond just image search. An article about dog training that includes images with alt text mentioning “golden retriever learning sit command” reinforces the page topic. The same article with images lacking alt text or using generic descriptions like “photo” misses opportunity to strengthen topical relevance.
Image file names provide secondary signals but do not replace alt text. A file named “golden-retriever-training.jpg” tells search engines something about the image, but alt text provides the explicit description. Use descriptive file names as backup signal, not as alt text substitute.
Surrounding content context helps search engines interpret ambiguous alt text. “Product photo” as alt text on a page clearly about running shoes gets associated with running shoes. The same alt text on a page with mixed content provides less clear signal. Specific alt text removes ambiguity that surrounding context might not resolve.
Google Lens and visual search technology continue advancing. Search engines increasingly understand images directly without relying solely on alt text. However, alt text remains important for accessibility, for reinforcing signals, and for cases where visual recognition fails or produces uncertain results. Do not assume visual AI eliminates alt text value.
Okafor, Search Data Analyst Focus: Image Search Performance
Image search traffic appears in Google Search Console under the Search type filter. Switching from Web to Image shows impressions, clicks, and positions specifically for image search results. This data reveals which images drive traffic and which alt text formulations correlate with image search visibility.
Query analysis for image search differs from web search patterns. Image searchers often use more visual and descriptive terms. “Red running shoes side view” differs from “best running shoes.” Alt text that matches visual query patterns earns image search visibility that generic alt text misses.
Click-through rates from image search depend on alt text appearing in image pack results. When Google shows image packs within web search results, the alt text sometimes appears as caption or tooltip. Compelling, accurate alt text can influence whether users click your image versus competitors’ images.
Crawl statistics reveal whether search engines successfully process your images. If images appear in crawl reports with errors or are excluded from indexing, alt text cannot help because the images are not being processed at all. Fix crawl issues before optimizing alt text.
Comparing pages with optimized alt text versus pages without shows directional impact on both image search and overall organic performance. Run controlled comparisons across similar page sets to measure alt text optimization value for your specific site and content type.
Chen, Content Strategist Focus: Writing Effective Descriptions
Alt text writing follows the principle of accurate description serving the page context. Ask what information the image conveys that matters for this specific page. Describe that information in natural language. A product image needs different alt text than the same product shown in a lifestyle context.
Specificity improves both accessibility and SEO value. “Shoes” tells users and search engines almost nothing. “Women’s Nike Air Max 90 in white and pink colorway” tells them exactly what they see. Specific descriptions serve blind users better and provide search engines with clear signals.
Avoid starting alt text with “image of” or “picture of.” Screen readers already announce that an image is present. Adding these phrases wastes the limited attention users have for alt text content. Start directly with the description.
Keyword inclusion should happen naturally, not forcefully. If the image genuinely shows a golden retriever, saying “golden retriever” in the alt text is both accurate and SEO-relevant. If the image shows a generic dog but the page is about golden retrievers, do not claim the image shows a golden retriever. That is inaccurate alt text that misleads both users and search engines.
Context determines appropriate detail level. A hero image representing the entire page topic warrants detailed alt text. A small icon indicating a feature needs minimal alt text. A decorative background image needs empty alt text. Match description depth to image importance.
Alt text is not the place for calls to action or marketing messages. “Click here to buy the best running shoes” is not a description of an image. It is marketing copy that belongs elsewhere. Alt text describes what appears in the image, not what you want users to do.
Santos, Web Developer Focus: Technical Implementation
Alt attributes must be present on every img tag, even when empty. The code <img src=”image.jpg”> without any alt attribute fails accessibility validation. The code <img src=”image.jpg” alt=””> with empty alt passes validation and correctly signals decorative images to screen readers.
CMS platforms handle alt text differently. WordPress provides alt text fields in the media library. Other platforms may require custom field configuration. Ensure your content management system provides alt text entry capability and that content creators know how to use it.
Lazy-loaded images require alt text on the actual img elements, not just on placeholders. If your lazy loading implementation swaps placeholder images for real images, verify that alt text transfers correctly. Some implementations lose alt text during the swap.
Background images set via CSS cannot have alt text. If an image conveys important information, it should be an img element with alt attribute, not a CSS background. Reserve CSS backgrounds for purely decorative visuals that need no description.
Image CDNs and optimization services sometimes strip or modify alt attributes. After implementing image optimization, verify that alt text survives the optimization process. Check rendered HTML, not just source templates.
SVG images embedded inline do not use alt attributes. Instead, use title and desc elements within the SVG markup to provide accessible descriptions. SVG images referenced via img tags can use standard alt attributes on the img element.
Responsive images using srcset and picture elements need alt text on the img element within the picture or on the img element using srcset. The alt attribute location remains consistent regardless of responsive image technique.
Foster, E-commerce SEO Manager Focus: Product Image Optimization
Product images drive e-commerce image search traffic. Users searching for products often start with image search to see what options look like before clicking through to purchase. Optimized alt text on product images captures this visual shopping behavior.
Product image alt text should include product name, key attributes visible in the image, and brand when relevant. “Nike Air Max 90 men’s running shoe in black and white, side profile view” describes the product, the visible attributes, and the image angle. This serves both users trying to understand the product and search engines trying to index it.
Multiple product images need differentiated alt text. A product page with five images should not have five identical alt text entries. “Nike Air Max 90 front view,” “Nike Air Max 90 heel detail,” “Nike Air Max 90 on foot” provides unique descriptions that capture different visual information and different search queries.
Lifestyle images showing products in use need contextual alt text. “Runner wearing Nike Air Max 90 on mountain trail” describes the scene and the product, helping image search connect this image with both product queries and contextual queries like “trail running.”
Zoom and alternate view images inherit base product information but add view-specific details. The main product alt text establishes product identity. Zoom and alternate view alt text references that identity while describing the specific view shown.
User-generated product images from reviews need alt text too. If your platform displays customer photos, ensure those images have alt text describing what appears. Automated solutions can prompt users to add descriptions or can apply generic descriptions based on product context.
Kowalski, Technical SEO Auditor Focus: Alt Text Auditing
Alt text audits extract image data from crawled pages and analyze completeness and quality. Crawling tools report images missing alt attributes, images with empty alt attributes, and the actual alt text content for populated attributes.
Missing alt attribute identification is highest priority. Images without any alt attribute fail accessibility requirements and miss SEO opportunity. Fix missing attributes before optimizing existing alt text content.
Empty alt attribute analysis determines whether empty values are appropriate. Empty alt is correct for decorative images. Empty alt is incorrect for images conveying information. Review empty alt instances to verify they represent genuinely decorative images.
Duplicate alt text detection reveals template issues or copy-paste problems. If hundreds of images have identical alt text, templates may be generating the same description regardless of actual image content. Investigate duplicates to determine whether unique descriptions are needed.
Alt text length analysis identifies extremes. Very short alt text under 10 characters may lack useful description. Very long alt text over 125 characters may exceed optimal length for screen readers. Review outliers for appropriateness.
Keyword stuffing detection flags alt text that reads as keyword lists rather than natural descriptions. “Running shoes best running shoes cheap running shoes buy running shoes” is keyword stuffing that helps neither accessibility nor SEO. Natural descriptions that happen to include relevant terms serve both purposes.
File name correlation check compares alt text against image file names. If alt text exactly matches file names, templates may be auto-generating alt text from file names rather than providing real descriptions. Auto-generated alt text from file names rarely provides optimal descriptions.
Bergstrom, SEO Strategist Focus: Competitive Image Analysis
Competitor image search analysis reveals opportunities in visual search results. Search for target queries in image search. Note which competitors appear, what images they use, and what alt text those images have. Inspect element reveals alt text for any image in search results.
Image search ranking patterns differ from web search. Sites with weak domain authority sometimes rank well in image search with properly optimized images. Image optimization represents opportunity to compete where web rankings prove difficult.
Visual content gaps appear when searching image results. If competitors show only product photos while users might want comparison charts, diagrams, or infographics, creating those visual assets with proper alt text captures underserved visual search demand.
Alt text quality comparison shows optimization levels across competitors. Many sites neglect image optimization entirely, leaving missing or generic alt text. Proper optimization provides competitive advantage in image search where competitors fail to compete.
Featured image selection in image packs depends partly on alt text relevance to query. Images with alt text closely matching search queries may earn featured positions over images with generic descriptions. Analyze which images earn featured positions and what their alt text contains.
Image freshness signals may influence image search rankings for time-sensitive queries. New images with relevant alt text may outrank older images. For topics where recency matters, creating fresh visual content with optimized alt text provides competitive opportunity.
Villanueva, Content Operations Manager Focus: Alt Text Workflows
Alt text creation belongs in content production workflows, not as an afterthought during technical audits. Content creators who add images should add alt text simultaneously. Separating these tasks creates gaps where images launch without descriptions.
Content briefs should specify alt text requirements. When assigning content that includes images, include guidance on what alt text should describe. Writers who know expectations produce better alt text than writers who guess or skip it entirely.
Editorial review should include alt text verification. Before content publishes, someone should confirm that all images have appropriate alt text. This checkpoint prevents missing and inadequate descriptions from reaching production.
Image libraries and digital asset management systems should store alt text with images. When the same image gets reused across pages, the stored alt text provides starting point for context-appropriate modifications. This prevents redundant description writing and ensures consistency.
Training content creators on alt text best practices improves baseline quality. Many writers do not understand alt text purpose or requirements. Brief training on accessibility principles, description techniques, and SEO considerations elevates organization-wide alt text quality.
Alt text review during site migrations prevents wholesale alt text loss. When moving content between platforms, verify that alt text transfers correctly. Many migrations lose alt text because it is stored differently across systems.
Documentation of alt text standards enables consistency. Define organizational conventions for alt text length, style, keyword handling, and decorative image treatment. Published standards give content creators clear guidance rather than leaving decisions to individual interpretation.
Synthesis
Expert perspectives on alt text converge on the fundamental dual purpose: accessibility for users who cannot see images and signals for search engines that cannot interpret images visually.
The accessibility voices emphasize that alt text exists first to serve blind users. Descriptions should convey what matters about images in their specific contexts. Decorative images need empty alt to avoid cluttering screen reader announcements. Length should match complexity without becoming burdensome.
Search system perspectives confirm that alt text remains important despite advancing visual recognition technology. Alt text provides explicit signals that reinforce page topics and enable image search ranking. File names and surrounding context provide supporting signals but do not replace explicit descriptions.
Content strategy voices establish principles for effective alt text writing. Specificity beats generality. Natural language beats keyword lists. Context determines appropriate detail level. Marketing messages do not belong in alt text.
Technical implementation perspectives cover the mechanics of proper alt text deployment across platforms and image types. Every img element needs an alt attribute. Lazy loading, responsive images, and CMSs create edge cases that require attention.
E-commerce perspectives highlight the commercial value of product image optimization. Product images with complete, accurate alt text capture image search traffic from visual shoppers. Multiple product images need differentiated descriptions.
Audit and competitive perspectives provide methods for assessing and improving alt text at scale. Crawl-based analysis reveals missing, duplicate, and problematic alt text. Competitor analysis reveals optimization gaps in image search.
Workflow perspectives emphasize that sustainable alt text quality requires process integration. Alt text belongs in content creation workflows, not retrofitted during technical audits. Training, standards, and editorial review maintain quality across organizations.
Frequently Asked Questions
What should alt text describe?
Alt text should describe what matters about the image in its specific context. Focus on information the image conveys that relates to the page content. A product image needs product details. An infographic needs its key message. A decorative image needs nothing.
How long should alt text be?
Aim for under 125 characters for most images, which is the length screen readers handle smoothly. Simple images need shorter descriptions. Complex images conveying substantial information may need longer descriptions or supplementary text elsewhere on the page.
Should I include keywords in alt text?
Include keywords only when they accurately describe what appears in the image. If the image genuinely shows a golden retriever, saying “golden retriever” is appropriate. Do not add keywords that do not describe the actual image content.
What is empty alt text and when should I use it?
Empty alt text uses alt=”” with nothing between the quotes. Use it for decorative images that add visual interest but convey no information. This tells screen readers to skip the image rather than announcing it.
Does alt text affect SEO rankings?
Yes. Alt text helps search engines understand image content for image search rankings. It also reinforces page topic signals that influence overall organic rankings. Missing alt text means missing signals that competitors may capture.
Should every image have alt text?
Every img element needs an alt attribute. Informational images need descriptive alt text. Decorative images need empty alt text. No img element should lack the alt attribute entirely.
What is the difference between alt text and image captions?
Alt text is metadata that appears only when images fail to load or when screen readers announce images. Captions are visible text that all users see alongside images. Both can exist on the same image and serve different purposes.
How do I write alt text for complex images like charts or infographics?
Summarize the key message or data point in the alt text. Provide detailed data in text form elsewhere on the page. Complex images may need both brief alt text and extended descriptions in surrounding content.