TL;DR: The HTML attribute that holds descriptive text for an image, used by screen readers and search engines to understand its content.
In a nutshell
Alt text describes what an image shows so visually impaired users hear it via screen readers, Google can rank it, and visitors still get context if it fails to load. Keep it natural, under 125 characters, and avoid stuffing keywords. A product photo might read: “Black running shoes with white sole and laces”.
Quick answer: The alt attribute is the HTML attribute that holds alternative text for an image. It’s read by screen readers for visually impaired users, used by search engines to understand image content, and shown if the image fails to load. Every meaningful image should have alt text describing what it shows.
What Is the ALT Attribute?
The ALT attribute (or alternative text) is an HTML attribute that describes the content of an image on a webpage. It’s not visible to most users but is crucial for both accessibility and SEO.
When search engines crawl your site, they can’t “see” images the way humans can. So, the ALT text provides a text-based description that helps search engines understand what the image is about. Google’s own Google Search Central guidelines on image SEO call this out as one of the most reliable signals about image content.
At BrisTechTonic, we ensure all images across our client sites are optimised with descriptive, keyword-relevant ALT text as part of our SEO audit process. It’s a small step that makes a big impact on search rankings and user experience.
Why ALT Text Is Important for SEO
Google can’t “see” images, but it can read the ALT text and use it to:
- Understand the context of the image
- Rank your images in Google Image Search
- Provide better results for users searching with Google Lens or visually impaired users
Google also uses ALT text as a ranking factor for content relevance. So, if you’re optimising your content but forgetting about your images, you’re missing out on valuable SEO opportunities. Pair this with broader image optimisation for the strongest result.
Best Practices for Writing ALT Text
Be Descriptive
Your ALT text should describe what’s in the image, as simply and clearly as possible. For example, if the image shows a person working on a laptop in a co-working space, you might write: “Person working at a desk in a modern coworking space with a laptop.”
Avoid Keyword Stuffing
While it’s tempting to stuff ALT text with keywords like “SEO consultant” or “SEO services,” don’t overdo it. The ALT text should still be natural and relevant to the image. Google can penalise pages for over-optimisation. The fundamentals are summarised in the Moz Beginner’s Guide to SEO.
Keep It Concise
Keep ALT text under 125 characters. Screen readers typically cut off longer descriptions, and search engines prefer concise, targeted descriptions.
Include Target Keywords (But Sparingly)
If it makes sense, include a relevant keyword in the ALT text. For example, if the image is related to your service page about SEO consultancy, it might say: “SEO consultant working on a website audit.”
How We Optimise ALT Text at BrisTechTonic
In our SEO packages, we ensure all images are optimised with relevant, clear ALT text. This includes:
- Writing unique descriptions for each image
- Using keyword-rich descriptions for important images
- Ensuring images across the site are consistent and user-focused
Our approach is also incorporated into our SEO Blueprint course, where we walk through best practices for image optimisation and why it matters for your rankings. It is also a routine check in any technical audit.
ALT Text and Accessibility
ALT text is a critical part of web accessibility. It provides a description of the image for people who use screen readers, helping them understand the content of the image. It’s required for compliance with accessibility standards such as WCAG (Web Content Accessibility Guidelines).
At BrisTechTonic, we treat accessibility with the same care as SEO, because everyone deserves to access your content, regardless of their physical abilities. This ties into broader user experience (UX) work.
Common Mistakes with ALT Text
- Using “image of” or “photo of”: There’s no need to preface your description with these phrases. Google already knows it’s an image.
- Keyword stuffing: Avoid overloading ALT text with keywords. Keep it relevant to the image and page content.
- Leaving ALT text blank: Every image should have an ALT attribute. If it’s decorative and doesn’t add content, you can use an empty ALT attribute (
alt=""), but don’t leave it out entirely.
Frequently Asked Questions
What goes in alt text?
A description of what the image shows, in natural language. For a product photo: "Black running shoes with white sole and laces". For a charts: "Bar chart showing organic traffic doubled between January and June". Match the description to what would help a user who can’t see the image.
Should alt text include keywords?
Where natural, yes. The alt text for your service page hero image can naturally include the focus keyword. Don’t force keywords; honest description first, keywords second when they fit. Stuffed alt text is detected and penalised.
What about decorative images?
Use empty alt text: alt="". This signals to screen readers that the image is purely decorative and they should skip it. Don’t omit the alt attribute entirely; an empty alt is different from no alt.
How long should alt text be?
Specific enough to describe the image, short enough to be read aloud quickly. Typically 5-15 words; up to 125 characters as a hard ceiling. Concise and informative beats verbose.
Take this further
Alt text is accessibility and SEO foundations. We audit alt text systematically because most sites have at least some images missing it.
Ready to apply this to your own site? Book a free discovery call, or explore our SEO strategy service.