The Complete Guide to Writing Effective Alt Text for Images

Imagine Sarah, a teacher who lost her sight five years ago. She loads your blog post with her screen reader. It skips right over the photo of your team brainstorming new ideas. Sarah hears gaps in the story. She closes the tab, frustrated. That photo held key details about your work culture.

Alt text fixes this. It’s a short text description hidden in the image code. Screen readers speak it aloud. Search engines read it too. In January 2026, with tighter WCAG rules and Google updates, good alt text boosts accessibility and rankings. About 16 million people in the UK live with sight loss. Millions more use screen readers daily worldwide.

This guide walks you through it all. You’ll learn what alt text does and why it matters. You’ll master core rules with examples. We’ll cover tricky cases, pitfalls, and tools to test your work. By the end, your site will welcome everyone and climb search results.

What Alt Text Does and Why It Counts

Alt text tells people and machines what an image shows when it can’t display. Think of it as a voice for your visuals. Without it, your site feels like a book with blank pages. A team meeting photo might just say nothing. Users miss the energy in the room.

It serves two main groups. Screen reader users get the full picture. Search engines index images better. Google pulls alt text into its image search results. Your photo of a sunny park picnic could rank for “team lunch outdoors”.

Sites without solid alt text lose trust. Readers sense something’s off. In 2026, Google’s algorithms favour accessible pages. WCAG 2.2 demands clear non-text content. Empty alt suits decorative flourishes, like background patterns. They add style, not info.

Key Wins for Users and Search Engines

Screen readers like NVDA turn alt text into speech. A blind user hears “Golden retriever fetches ball in green park”. They picture the joy, follow the post’s flow.

For SEO, alt text matches search terms. Say your e-commerce site sells bikes. Alt text “red mountain bike on rocky trail” hits queries like “trail bike”. It fits the page without copying nearby captions. Google rewards this match.

Take a product shot: red bike gleaming under lights. Bad alt: “bike”. Good: “red mountain bike with 27 gears on dirt path”. Users shop smarter. Your site appears in more searches.

Legal and Ethical Reasons to Get It Right

WCAG success criteria 1.1.1 require text alternatives for images. Fail it, and your site scores low on audits. UK firms face lawsuits over access barriers. One high-street brand paid out last year.

It’s simple ethics too. Everyone deserves your content. Good alt text builds loyalty. Readers return to inclusive sites. Check this guide on WCAG basics for compliance steps.

Core Rules for Writing Alt Text That Works

Start with the basics from 2026 guidelines. Keep it under 125 characters. Describe what you see and why it matters. Drop “image of” or “photo shows”. Lead with the subject.

Focus on subject, action, setting. A dog photo: not “dog pic”, but “brown labrador swims in lake at sunset”. Stay factual. No “cute pup”. Match the page context. If the post discusses pet training, add “labrador obeys sit command”.

For text in images, copy it word for word. A poster saying “Sale ends Friday” gets that exact phrase. Test spelling always. Screen readers stumble on errors.

Before: “Picture of a dog”. After: “Golden retriever plays fetch in park”. The good one paints a scene. Readers grasp purpose fast.

Prioritise essentials. What tells the story? A chart on sales growth: “bar graph shows 20% rise from 2024 to 2025”.

Make It Short, Clear, and to the Point

One or two sentences max. Screen readers cut off long ones. Lead with key facts. “Four colleagues share sandwiches in sunny park” works. It skips fluff like “happy group enjoys outdoor meal”.

Count characters. Tools flag overlimits. Short alt loads quick on mobiles too.

Skip Filler Words and Stay Neutral

Facts only. “Orange sunset over mountains” beats “stunning orange sunset”. Opinions distract. Neutral lets users form views.

Avoid vague terms. “Group of people” misses details. Say “three engineers test drone prototype”.

Tackle Special Images and Common Pitfalls

Some images need special handling. Decorative icons get empty alt: alt=””. They don’t add meaning.

Linked images describe both. “Map of London attractions. Links to tourist guide”. Users know where clicks lead.

Complex charts or infographics take a summary. “Pie chart: 40% sales from Europe, 30% Asia”. Expand details in nearby text.

2026 updates stress context for graphs. Google’s bots parse linked visuals better.

Pitfalls trip many. Too long text bores listeners. Repeating captions wastes space. Ignoring context confuses.

Checklist: What’s the image’s purpose? List key elements. Is it concise? Test with a reader.

Bad: “Image shows beautiful landscape”. Good: “Snow-capped Alps under blue sky”.

Decorative, Linked, and Complex Images

Decoratives: alt=”” keeps flow clean.

Linked: “Product photo: wireless headphones. View details”.

Complex: Short alt, full prose below. See best practices for alt automation.

Top Mistakes and Quick Fixes

Mistake: Filler like “photo of”. Fix: Jump to action.

Vague: “Animal”. Fix: “Tabby cat sleeps on windowsill”.

Adjectives: “Gorgeous meal”. Fix: “Grilled salmon with vegetables”.

Side-by-side:

Tools and Tests to Perfect Your Alt Text

Free tools spot issues fast. WAVE scans pages for missing alt. Lighthouse in Chrome audits accessibility scores.

Test with screen readers. Download NVDA for Windows. VoiceOver on Mac. Hear your alt aloud. Does it flow?

Browser dev tools show alt text. Right-click image, inspect. Edit live.

Routine: Add alt to new images. Run WAVE weekly. Tweak based on reads.

SEO bonus: Google Image Search loves it. Check this SEO checklist.

Audit your site today. Small changes yield big gains.

Conclusion

Alt text bridges sight gaps and lifts rankings. You now know its purpose, core rules, special cases, pitfalls, and testing tools. Write short, factual descriptions that match context.

Review your images this week. Add alt where needed. Watch access improve and traffic grow.

Picture a site everyone loves: Sarah stays, engages, shares. Your content reaches far.

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