You’ve spent hours writing your blog post. You’ve picked the perfect images. You’ve hit publish. And then you wait — but the traffic doesn’t come the way you hoped.
Here’s something most people miss: the images sitting right there on your page could be quietly hurting your SEO — simply because nobody wrote a single word to describe them.
That’s what alt text is for. And in this guide, we’re going to cover everything — what it is, why it matters more than most people realise, and exactly how to write it well.
What Is Image Alt Text, Really?
Alt text — short for alternative text — is a short written description that you attach to an image on a webpage. You don’t usually see it when the page loads normally. But it shows up in three important situations:
- When the image fails to load — maybe the file is broken or the user has a slow connection. Instead of a blank box, they see your description.
- When a screen reader reads the page — visually impaired users rely on screen readers that read out every element on the page, including your images.
- When a search engine crawls your page — Google’s bots cannot see images the way a human can. They read the alt text to understand what the image is about.
In your website’s HTML code, alt text looks like this:
<img src="red-running-shoes.jpg" alt="Woman wearing red running shoes on a forest trail">
That small piece of text — sitting quietly in the background — does a surprising amount of work for your website.
Why Alt Text Matters for SEO: The Real Story
Let’s be honest. When people first hear about alt text, they often think it’s a minor detail — something you add just to tick a box. But that thinking is costing websites real traffic every single day.
Here’s why alt text is genuinely important for SEO.
1. Google Cannot See Your Images
This is the most important thing to understand. When Google sends its crawlers to read your website, they process code and text. Images are just files — JPEGs, PNGs, WebPs. Google has made progress with visual understanding through AI, but the search engine still relies heavily on alt text to know what an image shows.
Without alt text, your image is essentially invisible to Google. It exists, yes, but it carries no SEO value. You’ve missed a chance to tell Google more about your page’s topic.
With good alt text, that same image becomes a piece of evidence. It supports your content. It helps Google understand the context of your page — and that can push you higher in search results.
2. Google Image Search Is a Real Traffic Source
Most people think about SEO purely in terms of regular web search. But Google Image Search is massive. Millions of people search for images every day — for recipes, products, tutorials, inspiration, and more.
When your images have descriptive alt text, they become eligible to appear in Google Image Search results. Someone searching for “how to tie a Windsor knot” might find your step-by-step tutorial image before they ever find your article. That image click brings them to your site.
Without alt text, your image has almost no chance of ranking in image search. You’re leaving that traffic on the table.
3. Alt Text Reinforces Your Page’s Topic
Search engines look for consistency. When your page is about “home office setup ideas,” they want to see that theme running through your headings, your text, your links — and yes, your images.
When every image on that page has relevant alt text — “minimalist home office desk with dual monitors,” “standing desk with wooden top and cable management” — it sends a consistent signal. Your page really is about what it says it’s about. That consistency builds topical authority and improves your chances of ranking.
4. It Affects Your Core Web Vitals Indirectly
Google has made page experience a ranking factor. Accessibility is part of a good page experience. When users with visual impairments can navigate your site properly — thanks to descriptive alt text — it reflects well on your site overall. It also reduces the chance of users bouncing because they can’t understand your content.
The Accessibility Side: Why It’s Not Just About SEO
It would be wrong to talk about alt text purely in terms of rankings and traffic. At its heart, alt text exists because the web should work for everyone.
Around 2.2 billion people worldwide have some form of visual impairment. Screen readers like JAWS, NVDA, and VoiceOver read web content aloud to these users. When they encounter an image without alt text, they either skip it entirely or read out something unhelpful like the filename — “IMG_4872.jpg” — which tells the listener absolutely nothing.
Good alt text creates an equal experience. A blind user reading your cooking blog should be able to understand that an image shows “a golden-brown sourdough loaf cooling on a wire rack” — not just encounter silence where a picture should be.
When you write great alt text, you’re doing something genuinely good. It matters beyond the algorithm.
How to Write Alt Text That Actually Works
Now we get to the practical part. Writing alt text isn’t complicated, but there’s definitely a right way and a wrong way. Here’s how to do it well.
Be Descriptive, But Concise
Your alt text should describe what’s actually in the image — specifically and clearly. Aim for around 8 to 15 words for most images. You don’t need to write a paragraph, but a single vague word won’t help anyone.
Too vague: alt="dog"
Much better: alt="Golden retriever puppy sitting on a green lawn in the afternoon sun"
The second version paints a picture. Anyone who can’t see the image now has a clear mental image of it.
Include Your Target Keyword — Naturally
Here’s where SEO and good writing meet. If your target keyword can genuinely and naturally fit into the description of the image, include it. Don’t force it. Don’t stuff it in awkwardly.
Forced (bad): alt="SEO alt text SEO tips SEO guide woman working on laptop"
Natural (good): alt="Woman writing SEO-optimised blog content on a laptop at a home desk"
The second version includes a relevant SEO phrase, but it reads like a real description. It’s useful for both screen readers and search engines.
Don’t Start With “Image of” or “Picture of”
Screen readers already announce that something is an image before they read the alt text. So starting your alt text with “image of” or “photo of” is redundant — it wastes your character count and sounds clunky.
Redundant: alt="Photo of a cup of coffee on a wooden table"
Cleaner: alt="Flat white coffee in a ceramic cup on a dark wooden table"
Jump straight into the description.
Write for the Context of the Page
The same image can have different alt text depending on where it appears. A photo of an apple on a nutrition website might need alt text like “Fresh red apple, a source of fibre and vitamin C.” On a cooking blog, the same image might work better as “Red apple on a wooden chopping board, ready for slicing.”
Think about what role the image plays in the content. What does someone need to know about this image to understand the page?
Different Images Need Different Approaches
Not all images are equal, and your alt text strategy should reflect that.
Informational images — images that add meaning to the page. These need full, descriptive alt text.
Decorative images — images used purely for visual styling that don’t add any meaning (like a background texture or a generic divider image). For these, use empty alt text: alt="". This tells screen readers to skip the image entirely, which is actually the right thing to do.
Images with text in them — infographics, screenshots, charts. Include the key information from the text in the alt text. If there’s a lot of text, consider also providing a text alternative or caption below the image.
Product images — be specific. Include the product name, colour, and any key details. alt="Nike Air Max 270 trainers in black and white, side view" works much better than alt="trainers".
Charts and graphs — describe what the chart shows, not just its type. alt="Bar chart showing UK coffee consumption rising 40% between 2015 and 2024" is far more useful than alt="bar chart".
Common Alt Text Mistakes to Avoid
Even experienced writers make these mistakes. Here’s what to watch out for.
Keyword stuffing. Writing alt="cheap flights cheap holidays cheap travel book cheap flights now" is exactly what Google’s guidelines warn against. It’s manipulative, unhelpful, and can actually harm your rankings.
Leaving it completely blank. Not adding alt text at all means you’re missing out on SEO value and failing visually impaired users. Make it a habit — every meaningful image gets alt text.
Writing the filename as alt text. Some content management systems auto-fill the alt text with the image filename: “IMG_2094.jpg” or “stock-photo-1234.jpeg.” That tells neither users nor search engines anything useful. Always write a proper description.
Being too long. If your alt text reads like a short story, trim it. Google has not confirmed a hard character limit, but best practice suggests keeping it under 125 characters. Get to the point.
Describing the wrong thing. If your image shows a woman hiking in the Lake District, don’t write alt text about hiking shoes just because that’s the page topic. Describe what’s actually there.
A Simple Process for Writing Alt Text at Scale
If you’re managing a blog or website with lots of images, here’s a straightforward approach:
- Audit your existing images. Use a tool like Screaming Frog or your CMS’s built-in SEO checker to find images with missing or weak alt text.
- Prioritise key pages first. Start with your highest-traffic pages and your product pages — these have the most to gain.
- Build it into your publishing workflow. Before any post goes live, alt text is added. Make it a checklist item, not an afterthought.
- Review periodically. As your keyword strategy evolves, old alt text may need updating.
What Good Alt Text Looks Like in Practice
Let’s look at a few real-world examples across different content types.
| Image | Weak Alt Text | Strong Alt Text |
|---|---|---|
| A sourdough loaf | “bread” | “Golden sourdough loaf with a scored crust, cooling on a wire rack” |
| A homepage hero image of a team | “team photo” | “Diverse team of five professionals collaborating around a meeting table” |
| An infographic about sleep | “infographic” | “Infographic showing that adults need 7–9 hours of sleep per night for optimal health” |
| A product shot of headphones | “headphones” | “Sony WH-1000XM5 wireless noise-cancelling headphones in black, front view” |
| A blog header image (decorative) | “header” | (empty alt text — it’s decorative) |
Final Thoughts: Small Text, Big Impact
Alt text might be one of the smallest pieces of copy you ever write — sometimes just ten words. But those ten words do important work. They help search engines understand your content. They open your website to millions of users who rely on screen readers. They give your images a chance to rank and drive real traffic.
The good news is that writing great alt text isn’t hard once you understand what it’s for. Be specific. Be natural. Think about the real person — or the search engine — on the other side. And make it a consistent habit, not an occasional afterthought.
Your images already say something. With good alt text, they say it to everyone.