Alt text & SEO: Everything you need to know

Images are no longer just decorative; they play a critical role in search engine optimisation, accessibility, user experience and brand trust. Alt text (also known as alt tags or alt attributes) is a simple HTML attribute that provides descriptive text for images – yet many websites still don’t use it well.

In this article, we’ll explain what alt text is, why it matters more than ever, how to write it properly and how to integrate it into your broader SEO strategy.

What is alt text?

• Definition: Alt text (short for “alternative text”), is an attribute added in the HTML img tag.
  Example: <img src="/dog-washing.jpg" data-alt="dog having a bubbly wash in Sydney backyard">.
• Purpose: Its main job is to describe what an image depicts when it can’t be displayed (broken link, slow connection, image disabled) or when it’s being accessed by non-visual means (screen readers for vision-impaired users).
• Other names: Alternative text, alt attribute, alt description. “Alt tag” is common but technically a misnomer – because the alt text lives in an attribute of the image tag, rather than being a separate tag.

Why alt text matters more than ever

1. Accessibility is now non-negotiable
   Many countries and jurisdictions have strengthened legal requirements for web accessibility. Alt text is a core accessibility feature: screen readers rely on it to convey meaning. Poor or missing alt text can lead to user frustration, complaints or even legal risk.
2. Search engines are smarter
   Modern search algorithms (eg. Google’s) leverage image recognition, machine learning and context to better understand what images are about. The alt attribute is one of several signals that help confirm that context. While it’s not a huge ranking factor by itself, it contributes to overall content quality and relevance.
3. Image search & visual search are growing
   Visual search tools (like Google Lens) and image search result carousels are more prominent in SERPs. Well-described images are more likely to show up. If someone uses an image-based query (“dog washing techniques”), having descriptive alt text helps.
4. User experience / site speed & SEO tie-ins
   If images fail to load (slow connection, errors), alt text provides fallback content. Using good alt text as part of well-optimised, responsive images enhances usability. Search engines reward better UX.
5. Mobile-first indexing & low-bandwidth devices
   Many users on mobile or with limited data might disable images. Similarly, page load times are even more critical now, especially considering Core Web Vitals. Alt text supports graceful degradation of design.

Common misconceptions

• Alt text = SEO keyword stuffing: No. Using alt text purely to jam keywords is counterproductive. Search engines can penalize over-optimisation or see it as spammy.
• Every image has to have a keyword in alt text: Not necessarily. Sometimes decorative or purely stylistic images should have empty alt text (e.g. alt="") or be coded as CSS background images.
• Alt text alone will rank you high in image search: Alt text helps, but it’s part of a broader set of optimisations – image filename, captions, page content around the image, site structure, schema, image format & performance, etc.

How to write good alt text – best practices

  
Here are best practices that reflect current industry standards, taking into account recent algorithm updates, accessibility guidelines and performance priorities:

Technical how-to & tools

Here are actionable steps and tools to help you check, fix and maintain alt text across your site.

• Inspect manually: In browser dev tools (“Inspect Element”) check if the alt attribute is present for images.
• CMS usage: Most CMSs (WordPress, Shopify, Joomla, etc) allow adding alt text when uploading images. Make it part of workflow – don’t skip.
• Accessibility checkers: Tools like WAVE, Lighthouse (built into Chrome DevTools), Axe and others will flag missing or inappropriate alt text.
• SEO / site audit tools: Screaming Frog, Ahrefs, Semrush, Moz, etc. can crawl a site and report images without alt text, long alt text or alt text that appears duplicated.
• Batch updates: If you have many images missing alt text, you might use plugins or scripts (carefully) to update them in bulk. But manual review is ideal for key images.

Alt text and SEO: What is its weight?

While alt text is not one single magic bullet, it contributes across several SEO & web performance dimensions:

1. Relevance signal
   Alt text helps search engines understand what the page (and the image) is about. It works in conjunction with page title, headings, image captions, surrounding textual content.
2. Image search visibility
   Google Images (and other engines) can show your content in image carousels or image-based results. Good alt text increases the chance images will appear there.
3. Accessibility and user trust
   Users appreciate well-described images; visually impaired users rely on it. Sites that do accessibility well often see improved user metrics (lower bounce rates, more time on page), which indirectly help SEO.
4. UX and fallback content
   For slow or unreliable connections, or devices that don’t display images, alt text provides fallback so content still “makes sense.” Sites that degrade gracefully tend to perform better in overall user satisfaction.
5. Compliance and risk mitigation
   Ensuring images have appropriate alt text reduces risk from accessibility complaints or regulatory issues in places with strong Web Content Accessibility Guidelines (WCAG) enforcement.

Examples of good vs poor alt text

Alt text + SEO strategy: Integrations & advanced tips

To really maximise the impact of your alt text, it helps to embed it into a holistic content and technical strategy:

• Use schema markup
  For images relevant to products, reviews, recipes, etc, structured data (Schema.org) can provide additional signals. For example, product schema can include images; Google often uses image schema for “rich results.”
• Optimise image size and performance
  Regardless of how good your alt text is, if your images make your site slow (no compression, no resizing, outdated formats), you’ll suffer. Use modern formats (WebP, AVIF), responsive image markup, lazy loading. Read more about optimising images for your website >>
• Lazy-loading and prioritising “hero” images
  Let less critical images load later; make sure primary images load quickly. Primary images need strong alt text since these are most prominent.
• Consistent style
  If you have multiple authors, have guidelines or style sheets for alt text (tone, length, format). This ensures consistency across site pages.
• Local SEO & localisation
  If your business is local, add geographic detail appropriately (when relevant). For example, “Italian restaurant interior in Paddington, Brisbane” rather than just “restaurant interior.”
• Image sitemaps
  If your site has lots of images (eg. e-commerce, photography), including them in an image sitemap can help search engines discover and index them.

What to avoid & common pitfalls

• Keyword stuffing – forcing in keywords makes alt text unnatural and risks being penalised.
• Overly long alt text – too verbose is as bad as too vague. If the alt text becomes multiple sentences for decorative or non-critical images, trim down.
• Duplicate alt text across many images – if you use the same phrase repeatedly, you lose specificity.
• Ignoring context – alt text that doesn’t align with page content looks out of place; can confuse users and search engines.
• Treating alt text as an SEO checkbox – it should be about helping users (accessibility, clarity), with SEO benefits following.

Recent developments (2023–2025)

To keep you current, here are a few more recent shifts or things to watch for:

• AI & image recognition: Google, Microsoft, and others are increasingly using visual understanding (eg. identifying objects, faces, text in images). Alt text helps confirm what the system “sees,” especially when the automatic vision system has some uncertainty.
• WCAG 2.2 / 3.0 guidelines: Newer accessibility standards emphasise alt text quality more strongly. For example, making sure that image descriptions are meaningful and helpful.
• Voice assistants / smart speakers: As more content is consumed via voice interfaces, alt text helps when images are read out in audio-only environments.
• Privacy / data concerns: Be mindful not to include personal or sensitive information in alt text (or embedding in image files or metadata) unless legally compliant.

Putting it all together: A checklist for alt text implementation

Here’s a ready-to-use checklist you or your web team can follow to audit and improve alt text across your site:

1. Inventory audit
   - Gather all images across your site
   - Identify those missing alt attributes
   - Flag decorative images vs content images
2. Define style & tone
   - Decide ideal length (eg. 5–15 words, or ~125 characters)
   - Establish voice (formal vs casual)
   - Decide when to include location/context etc
3. Update existing images
   - Prioritise top-performing pages / pages important for conversions
   - Add or correct alt text; check for keyword relevance
4. Workflow integration
   - Make adding alt text part of the process when uploading images
   - Train content creators / designers in best practices
5. Testing & monitoring
   - Use automated tools (Lighthouse, Screaming Frog, etc.) to flag missing or bad alt text
   - Review user metrics: time on page, bounce rates, usability feedback
   - Check Image Search / Rich Results visibility
6. Ongoing maintenance
   - Regular audits (quarterly or biannually)
   - Update alt text when updating images or repurposing content

Alt text remains a small but powerful tool in both SEO and usability/accessibility. It may not be the single strongest ranking signal – after all, content quality, site speed, mobile-friendliness, backlinks, etc carry big weight – but it plays a vital supporting role.

Used properly, it enhances your content, improves accessibility, helps with image search visibility and contributes to a stronger overall site health.

If you invest a little time to do alt text well – making it descriptive, contextual and user-focused – you’ll be rewarded with better engagement, fewer UX barriers, and improved search engine performance.