Search engines cannot interpret images in the same way they interpret text. To understand what an image shows, they rely on elements such as the alt attribute, or alt text, which describes the image in words.
This attribute serves a dual purpose. On the one hand, it improves accessibility by allowing screen readers to convey visual information to users with visual impairments. On the other, it helps search engines index images correctly, which can influence SEO.
In this article, I’ll focus on what alt text is, why it matters, and how to write effective alt text. If you’re looking for a more general guide on image SEO, I recommend reading my other article on image SEO.
Contents
What is the alt attribute?
The alt attribute, or alt text, is alternative text added to images on a web page to describe their content. Its main purpose is to provide information when the image cannot be displayed, either because of a loading error or because the user is relying on a screen reader. Although people often refer to it as a “tag”, it is actually an attribute of the element in HTML.
Using alt text not only improves accessibility, but also helps search engines understand the context of an image. Unlike visible page content, images cannot be interpreted directly by search engines, so they depend on attributes such as alt text to understand their relevance.
It is also important not to confuse the alt attribute with the title attribute. Alt text describes the image for accessibility and SEO purposes, while title is the text that may appear as a tooltip in some browsers when the cursor hovers over the image. Both can coexist, but alt text is the one that really matters for accessibility and image optimization.
Here is a simple example of alt text in HTML:
<img src="product-trainers.jpg" alt="White sports trainers with blue details" />In this example, the alt text clearly describes the image and makes it easier for both search engines and users with visual impairments to understand what it shows.
Why alt text matters for SEO
The alt attribute plays an important role in SEO because it helps search engines interpret the content of an image. Even though Google has improved its ability to recognize visual elements, it still relies on textual descriptions to index images properly. Good alt text makes that easier and can improve a website’s visibility in image search results.
Alt text also affects user experience. A page with clear, descriptive image information is more accessible and easier to use, which can contribute to stronger engagement and a better overall experience.
Another important point is traffic from Google Images. If an image has relevant, well-written alt text, it has a better chance of appearing in image search results and driving additional visits to the site. This is especially useful for e-commerce websites, visual blogs, and any site that depends on organic search visibility to attract users.
Why the alt attribute matters for accessibility and usability
The alt attribute is not only important for SEO. It also plays a key role in web accessibility. Its main purpose is to provide a textual description of images so screen readers can communicate that information to users with visual impairments. Without appropriate alt text, those users may miss part of the content entirely, which affects their browsing experience.
From a usability point of view, alt text also improves the general user experience. If an image fails to load because of a server issue or a slow connection, the alternative text can appear in its place and give the user context about what should have been there. This is especially useful on pages where images have an informative or functional purpose, such as buttons, diagrams, or infographics.
In broader SEO terms, accessibility is increasingly relevant because it is closely tied to user experience. Optimizing alt text not only helps search engines understand image content, but also makes the website more inclusive and easier to use.
Tips for writing effective alt text
Writing effective alt text is not just about adding keywords. It is about describing the image in a clear and useful way. Good alt text should be concise, relevant, and informative without becoming too long. A few practical recommendations:
- Describe the image accurately: Think about how you would explain the image to someone who cannot see it. For example, instead of writing “dog”, a better alt text would be “Labrador dog playing with a ball in the park”.
- Keep it brief but informative: In most cases, a short phrase is enough.
- Include keywords naturally: If the image is relevant to a specific search, it can make sense to include a keyword, but without forcing it. A poor example would be something like “Nike running shoes cheap sale online store”.
- Use alt text only when necessary: Not every image needs descriptive alt text. If the image is purely decorative, the best option is usually an empty alt attribute: alt=””.
- Avoid starting with “Image of…” or “Photo of…”: Screen readers and search engines already know it is an image, so that wording adds no value.
- Avoid keyword stuffing: Overloading alt text with keywords makes it less useful and less natural.
- Avoid alt text that is too generic: Terms such as “nice image”, “logo”, or “product” do not provide meaningful context.
Following these principles can improve both accessibility and image visibility in search.
How to add alt text to an image correctly
The alt attribute can be added in different ways, depending on the system you use to manage your content. Below are the most common ones.
Add alt text in HTML
If you work directly in HTML, you can add alt text manually inside the <img> element. This allows search engines and users relying on assistive technology to understand what the image shows.
<img src="mountain-gallery.jpg" alt="Panoramic mountain view at sunrise with fog in the valley" />In this example, the description is clear and provides useful visual context. Alt text should be specific enough to explain the image properly, but there is no need to make it excessively detailed.
Add alt text in WordPress
If you use WordPress, adding alt text is straightforward and is usually done through the Media Library. When you upload an image, WordPress gives you a dedicated field for alt text. Once completed, that text is then added automatically to the HTML when the image is inserted into a post or page.
The usual process is:
- Go to Media and select or upload an image.
- Find the Alternative Text field in the image details.
- Write a clear description of the image.
- Save or update the image settings.
This is useful because it helps ensure images are properly optimized without having to edit code manually.
Add alt text in other platforms or CMSs
Most major e-commerce platforms and CMSs also allow you to add alt text easily. The exact process varies slightly, but the goal is always the same: provide a useful and relevant description of the image. Some common examples are:
- Shopify: Alt text can be added in the product image settings. Each product image should ideally have unique alt text that describes it accurately.
- Wix: You can select the image in the editor and then add alt text from the image settings panel.
- PrestaShop: Alt text can be assigned from the product page when images are uploaded to the product gallery.
- Magento: Alt text can be added in the product management section, within the image description settings.
- Squarespace: In many cases Squarespace handles some image settings automatically, but you can still customize alt text in the image configuration for products, galleries, or images placed in content.
Although the interface changes from one platform to another, the principle is the same: give the image a description that is genuinely useful for both users and search engines.
Tools to view and analyse alt text
There are different tools that can help you review and optimize alt text across a website. These tools are useful not only for checking whether images have alt text, but also for spotting cases where the descriptions are missing, duplicated, or too weak.
SEO-focused tools
SEO tools such as Screaming Frog SEO Spider, Ahrefs, and Semrush can crawl a website and identify whether images include an alt attribute. They also make it easier to generate reports and fix issues at scale.
- Screaming Frog SEO Spider: Lets you crawl images, review alt text, and export results to CSV so you can identify missing or weak descriptions more easily.
- Ahrefs and Semrush: These tools also support site audits and can help surface image-related optimization issues, including problems with alt text.
Web accessibility evaluators and validators
Accessibility tools are also important when auditing alt text, since they help validate whether a page is usable for people with visual impairments and whether image descriptions are implemented correctly.
- WAVE (Web Accessibility Evaluation Tool): A free tool that analyses a page and flags accessibility issues, including images missing alternative text.
- axe Accessibility Checker: A browser extension that evaluates accessibility issues in detail, including image-related problems. It is especially useful for developers and designers.
- Google Lighthouse: Lighthouse includes accessibility audits and can identify images without alt text or with inadequate descriptions.
Using these tools helps you manage both the technical and content sides of alt text more effectively, making sure images are accessible and better optimized overall.
In the end, the alt attribute is essential for improving both accessibility and SEO. By using descriptive and relevant alt text, you help search engines understand your images better and make your content easier to access for users with visual impairments. Auditing and improving alt text regularly is a simple but worthwhile part of maintaining a better website.
