Alt text is a short description added to images in your website’s HTML code that tells search engines and screen readers what the image shows.
Writing good alt text helps your images appear in Google Image Search and supports your page’s rankings for relevant keywords.
Keep alt text under 125 characters, describe the image honestly, and include a keyword only where it fits naturally.
Every meaningful image on your site needs alt text, but decorative images (like borders or spacers) should have empty alt attributes.
You can add alt text in WordPress through the media library or by editing images directly within your pages and posts.
You have uploaded images to your website, chosen good file names, and compressed them so they load quickly.
But there is one more step that many small business owners skip: writing alt text.
Alt text is a short written description attached to an image in your website’s HTML code that tells search engines and screen readers what the image shows. This small detail plays a bigger role in your search rankings than you might expect.
Alt text (short for alternative text) does two things at once.
It tells Google what your image shows, which helps your pages and images appear in search results. And it makes your site accessible to visitors who use screen readers, giving them a text description when they cannot see the picture itself.
Google’s own image SEO documentation describes descriptive alt text as one of the most important signals they use to understand images on the web.
Getting alt text right is a quick win for small business websites.
It costs nothing, takes a few minutes per image, and supports both your on-page SEO and your legal accessibility obligations. This guide covers what alt text is, how to write it well, and how to add it in WordPress.
Table of Contents
What Is Alt Text and Why Does It Matter for SEO?
Alt text is a piece of HTML code attached to an image on your website.
When a browser cannot display an image (because of a slow connection, a broken file, or a screen reader being used), the alt text appears instead.
In the code, it looks like this:
<img src="plumber-fixing-tap.jpg" alt="Plumber repairing a leaking kitchen tap in a London home">
The text inside the alt="" attribute is your alt text.
How do search engines use alt text?
Google cannot see images the way humans do. While image recognition technology has improved, search engines still rely heavily on text-based signals to understand what an image shows.
Alt text is the primary way you tell Google what your picture is about.
It supports your page’s relevance for the keywords and topics you cover, and it gives your image a chance to appear in Google Image Search results, driving additional traffic to your site.
Google’s Search Central documentation advises website owners to write useful, descriptive alt text that uses keywords appropriately and relates to the surrounding content on the page.
Who uses alt text?
Alt text serves several groups of people and systems:
Screen reader users – People with visual impairments rely on screen readers like JAWS or VoiceOver, which read alt text aloud so they understand what an image shows. In the UK, the Equality Act 2010 requires businesses to make reasonable adjustments for disabled users, and providing alt text is considered a basic accessibility standard under WCAG (Web Content Accessibility Guidelines).
Search engine crawlers – Googlebot and other search engine bots read alt text to index and understand your images.
Users with slow connections – When images fail to load, alt text displays in place of the image so visitors still get context.
AI search systems – Tools like ChatGPT, Perplexity, and Google’s AI Overviews also read alt text when processing your web pages, making it relevant for AI search visibility too.
Does Adding Alt Text Improve SEO?
Yes, but with a sensible caveat.
Alt text is a confirmed ranking signal for Google Image Search. Google has stated that alt text helps them understand what images are about and how they relate to surrounding content.
For your main page rankings in standard Google search, alt text plays a smaller but still useful supporting role.
How does alt text support your rankings?
Think of alt text as one piece of a larger puzzle.
On its own, adding alt text to a single image will not catapult your page to position one. But when every image on your site has accurate, keyword-relevant alt text, you give Google consistent signals about your content’s topic.
Over time, this adds up.
Testing by Shaun Anderson at Hobo Web, who ran alt text indexing experiments between 2011 and 2018, found that Google counts roughly the first 16 words of alt text as a ranking signal for web search.
For Google Image Search, it indexes even more of the text. So you have enough room to write a proper, useful description that also contains a relevant keyword naturally.
Image search is where alt text has the most direct impact.
If you sell products, run a portfolio site, or publish image-heavy content, proper alt text can bring in traffic that competitors miss entirely.
Google Image Search handles billions of queries each month. A proportion of those searchers click through to the source website, giving you traffic that text-only SEO efforts miss.
How to Write Good Alt Text for SEO
Writing effective alt text is not complicated, but it does require thought. Here are the principles that make a real difference.
Be specific and descriptive
Describe what the image actually shows.
If it is a photo of your shop front, do not write “shop” or “image of building”. Instead, try something like “Front entrance of Smith’s Bakery on the high street in Guildford”. The more specific you are, the more useful the description is for both screen reader users and search engines.
Include keywords naturally
If your page targets a particular keyword, and the image genuinely relates to that keyword, include it in the alt text.
But do not force it.
Google warns against keyword stuffing in alt attributes, and it can result in your site being flagged as spam. The keyword should read naturally within the description, not feel bolted on.
Good example: “Small business owner updating WordPress website on a laptop” Bad example: “WordPress SEO website design small business WordPress expert UK”
Keep it concise
Aim for under 125 characters.
Some screen readers cut off alt text at around this length, and overly long descriptions become unhelpful. You do not need to describe every minor detail. Focus on what matters: what the image shows and why it is on the page.
Skip “image of” or “photo of”
Screen readers already announce that an element is an image before reading the alt text. Starting with “image of” or “picture of” is redundant and wastes characters. Describe the content directly instead.
Consider the context
The same image might need different alt text depending on where it appears.
A photo of a laptop on a page about remote working should describe the work scenario. That same photo on a page reviewing the laptop model should focus on the product itself.
The question to keep in mind is: why is this image here, and what does it add for the reader?
How Do You Add Alt Text in WordPress?
If you run a WordPress site (and most UK small businesses do), adding alt text is straightforward.
Adding alt text through the media library
- Go to Media > Library in your WordPress dashboard.
- Click on the image you want to edit.
- You will see a field labelled Alt Text on the right-hand side.
- Type your description and click Save.
This alt text will apply wherever that image is used across your site.
Adding alt text within a page or post
- Open the page or post in the WordPress editor.
- Click on the image you want to edit.
- In the block settings panel on the right, look for the Alt Text field.
- Enter your description.
If you use the Yoast SEO plugin, it checks whether your images include alt text containing your focus keyword and flags missing alt attributes during content analysis.
How do you check for missing alt text across your site?
You can use free tools like Screaming Frog’s SEO Spider to crawl your website and find images without alt text.
This is worth doing if you have an older site where images were uploaded without descriptions. Fixing missing alt text is one of the simplest on-page SEO improvements you can make.
You will also find that an SEO Audit will also look at image alt tags, right across your website.
Which Image Format Is Best for SEO?
Your image format affects page speed, which is an important ranking factor.
Here is a quick comparison of the formats most relevant to small business websites:
- WebP is the current recommended format. According to Google’s own testing, WebP images are 25-34% smaller than comparable JPEG images at equivalent quality, meaning faster page loads and better Core Web Vitals scores. Most modern browsers support it, and WordPress has supported WebP uploads since version 5.8.
- JPEG works well for photographs and complex images with many colours. It is widely supported and familiar.
- PNG is best for images that need transparent backgrounds, like logos and icons. Files tend to be larger than JPEG or WebP.
- SVG is ideal for logos, icons, and simple graphics. It scales to any size without losing quality.
- AVIF is a newer format with even better compression than WebP. Browser support is growing but not yet universal.
For most small business sites, converting your main images to WebP while keeping original formats as fallbacks is a practical approach. Whichever format you choose, compress your images before uploading them.
Tools like TinyPNG or Squoosh are free and effective.
How Should You Write Alt Text for a Logo?
Logos are a special case.
Your site logo appears on every page, usually linking to the homepage. The alt text should identify the company, not describe the visual design of the logo.
Good logo alt text: “Respect Experts – WordPress and SEO specialists” Less useful: “Red and white logo with company name in bold font”
If the logo is purely decorative (like a small design element that adds no meaning), you can use an empty alt attribute (alt=""). This tells screen readers to skip the image entirely, which avoids cluttering the experience for users who rely on assistive technology.
For your main site logo in the header, keep the alt text simple: your business name, optionally followed by a brief descriptor of what you do.
How Long Should Alt Text Be?
There is no strict character limit set by Google, but practical guidelines exist.
Aim for 10 to 15 words, or roughly 80 to 125 characters. This gives you enough room to describe the image meaningfully and include a relevant keyword without going overboard.
Very short alt text (like “dog” or “graph”) wastes an opportunity.
Very long alt text (two or three sentences) becomes unhelpful and may get truncated by screen readers. A single, specific phrase or sentence hits the sweet spot.
The W3C (World Wide Web Consortium), which sets web accessibility standards, suggests a useful test: imagine you are reading the web page aloud to someone over the phone.
Whatever you would say to describe the image in that conversation is probably about the right length and level of detail.
When Should You Use Alt Text?
Not every image on your site needs descriptive alt text.
Here is a simple guide:
Add alt text to:
- Product photos
- Team photos and headshots
- Images that illustrate or support your content
- Infographics and charts
- Screenshots used in tutorials
- Your main site logo
Use empty alt text (alt=””) for:
- Decorative borders and dividers
- Background patterns
- Icons that already sit next to visible text labels
- Spacer images
Using empty alt attributes for decorative images is not lazy. It is correct practice. Screen readers skip images with empty alt text, which makes the browsing experience smoother for people who rely on them.
Can AI Generate Alt Text?
Yes. Several tools now use artificial intelligence to generate alt text automatically.
WordPress plugins like AltText.ai and built-in features in Microsoft Office and some content management systems can analyse images and produce descriptions.
Where AI alt text works well
AI tools are genuinely useful for large sites with hundreds or thousands of images that currently lack alt text. They can process your media library in bulk and produce a reasonable first draft for each image.
For straightforward product photos and standard imagery, the results are often accurate enough to use with minor edits.
Where human review still matters
AI-generated alt text has its limitations.
Google’s John Mueller addressed this directly on Reddit in 2024, explaining that while AI can recognise what is in an image, it cannot provide the context for how that image fits into the page’s content.
The tools describe what they see, but they miss your target keywords, your page topic, and why you chose that particular image.
An AI might describe a chart as “bar graph with coloured sections” when what your reader needs is “Monthly website traffic figures showing 40% growth between January and June 2025”.
For your most important pages (homepage, service pages, key blog posts), writing alt text by hand gives you better results.
At the very least, review and edit what AI produces. Let automation handle the bulk work, then refine the descriptions on pages that matter most to your business.
Does Google Actually Look at Alt Text?
Yes, and Google has been clear about this. Their image SEO documentation states that alt text helps them understand what an image is about and how it connects to the content on the page.
John Mueller, a Google Search Advocate, stated on Twitter in 2018: “Alt text is extremely helpful for Google Images, if you want your images to rank there.” He has since reinforced this position in multiple public discussions.
Google uses alt text in several ways:
- To determine what an image shows for Google Image Search indexing
- To understand the topic and relevance of the page the image sits on
- To provide context when generating image search results and AI Overviews
- To assess the overall quality and accessibility of your website
The takeaway is simple. If Google takes the time to read and use your alt text, you should take the time to write it well.
What Are the Most Common Alt Text Mistakes?
Knowing what not to do is just as helpful as knowing what works.
Leaving alt text blank
This is the most common mistake.
The WebAIM Million 2025 report, which analysed one million of the web’s most popular homepages, found that 18.5% of all images lacked alt text entirely, and nearly one third had missing, questionable, or repetitive descriptions.
Every meaningful image should have a description.
Keyword stuffing
Writing “plumber London emergency plumber London plumbing services” as alt text hurts you rather than helps. Google treats this as spam, and it creates a terrible experience for screen reader users.
Using the file name as alt text
“IMG_4523.jpg” tells nobody anything. If you have not named your image files descriptively, do not rely on them as alt text substitutes.
Writing the same alt text for every image
Each image should have unique alt text that describes what that specific image shows. Copying and pasting the same description across multiple images is a wasted opportunity and may look like spam to search engines.
Frequently Asked Questions
SEO alt text is the descriptive text added to an image’s HTML code. It tells search engines what the image shows, helping it appear in image search results and supporting the page’s relevance for related keywords. Good alt text also makes your site accessible to visitors using screen readers.
Yes. Alt text is a confirmed ranking signal for Google Image Search and supports your page’s relevance in standard search results. It is a small factor on its own, but combined with other on-page signals, it contributes to how Google understands your content.
Describe the image honestly in 10 to 15 words. Include a relevant keyword if it fits naturally, skip phrases like “image of” or “photo of”, and focus on what the image shows and why it matters in the context of the page.
Include a clear, specific description of what the image shows. Focus on the subject, any relevant details (like location, product name, or action), and the image’s purpose on the page. Avoid vague descriptions like “photo” or “banner”.
Add descriptive alt text to every image that conveys meaning, including product photos, team images, illustrations, charts, and screenshots. Use empty alt text (alt=””) for purely decorative images like borders and background patterns.
WebP is currently the strongest choice for most websites. It delivers high quality at smaller file sizes than JPEG or PNG, which helps your page load faster. Faster pages tend to rank better, and WordPress has supported WebP since version 5.8.
Use your business name plus a brief descriptor. For example, “Smith’s Bakery, artisan bread and cakes in Guildford”. Do not describe the visual design of the logo itself. Keep it simple and focused on identifying the business.
Google has confirmed on multiple occasions that they read and use alt text. It forms part of how they index images, understand page content, and generate search results. Their documentation recommends writing useful, descriptive alt text for every meaningful image.
Yes. Tools like AltText.ai and built-in features in WordPress plugins can generate alt text automatically using image recognition. They work well for bulk processing, but you should review and edit the results for important pages, since AI cannot understand your page context or keyword targets.