If you’ve ever added an image to a website, you’ve likely seen the term “alt tag” pop up. But what is an alt tag, and why does it matter so much in 2025?

Alt tags, also known as alt attributes, are far more than just a box to fill in. They’re essential for accessibility, help boost your search rankings, and improve the overall browsing experience for users who may not see your images at all. With accessibility becoming more than just a buzzword and search engines getting smarter by the day, alt tags now carry real weight.

In this guide, we’re not just explaining what they are – we’ll show you how to write them properly, why they matter, and how to make them work for both your users and your SEO.

What Is An Alt Tag For An Image And Why Do We Use It?

An alt tag, short for alternative text, is a small line of text added to the HTML of an image. Its main job is to describe what the image shows in case it can’t be viewed, either because the user has a visual impairment, their internet connection is slow, or their browser doesn’t support images.

These descriptions aren’t just helpful; they’re necessary. Screen readers rely on alt attributes to convey visual content to users who can’t see it. Without them, those users are left guessing.

Search engines also use alt tags to understand what an image is about, which is why good alt text can help your content appear in image search results. It’s a win-win for accessibility and SEO.

While people often say “alt tag,” the correct technical term is “alt attribute.” It’s part of the HTML code that defines how an image behaves and is described.

For example:

In this snippet, the alt part is the attribute, and the text inside the quotation marks is the alternative description. The phrase alt tags on images is commonly used in conversation, but what you’re really adding is an alt attribute.

Understanding this small difference helps you speak the same language as developers and ensures your site meets both technical and legal standards (and helps answers what is an alt tag for an image?).

Why Alt Tags Matter For Accessibility

Accessibility isn’t optional. Laws like the Equality Act in the UK and the Americans with Disabilities Act (ADA) in the US mean that websites must be usable by everyone – including people who rely on assistive technologies.

When someone uses a screen reader, it reads aloud the alt attribute associated with an image. If the alt text is missing or poorly written, that person misses out on valuable information.

This is especially critical on e-commerce sites where an image may convey product details. A meaningful alt tag can provide enough context to make a purchase decision – whereas an empty or generic one can leave the user confused or excluded.

By ensuring every image has a relevant alt tag, you’re making your website more inclusive, ethical, and legally sound.

The SEO Benefits Of Using Alt Attributes Correctly

Search engines can’t “see” images the way humans do. They rely on cues – like file names, surrounding text, and most importantly, the alt attribute – to interpret what the image represents.

When you use clear, descriptive alt text, it boosts your chances of appearing in Google Images and improves your page’s overall relevance. This is especially useful if your content includes infographics, charts, or custom visuals (which might be one of the reasons you’ve googled ‘what is an alt tag for an image ‘ – right?).

However, alt tags should never be used to cram in keywords. Over-optimising makes them unreadable and defeats their purpose. Google penalises this kind of behaviour, and it doesn’t help users either.

A well-written alt tag balances clarity with conciseness. It’s not about tricking search engines; it’s about helping them understand what’s actually there.

How To Write Good Alt Text: Practical Examples

Writing alt text isn’t difficult, but it does take thought. A good rule of thumb is to describe what’s important about the image as if you were explaining it to someone who can’t see it.

Let’s look at a few examples:

• ❌ Bad alt text: image123.jpg

• ✅ Good alt text: Elderly couple holding hands in a park

• ❌ Too vague: Picture of event

• ✅ Better: Crowd gathered at the 2025 Brighton Tech Conference

Notice how good alt text focuses on the purpose of the image, not just its appearance. If the image is purely decorative, you can leave the alt attribute empty (alt="") so that screen readers skip it entirely.

What you’re aiming for is clarity, accuracy, and a user-friendly description – not an SEO hack.

Common Mistakes People Make With Alt Tags

The most frequent mistake is not using them at all. If you upload an image and skip the alt attribute, users relying on screen readers won’t know it’s there, and you miss a valuable SEO opportunity.

Another error is keyword stuffing. Writing something like “SEO tips SEO image SEO tricks SEO blog” in the alt tag won’t help you rank – it might even hurt your site.

Using generic text like “picture” or “image” isn’t useful either. The alt tag should describe the content, not the medium.

And finally, duplicating alt text across multiple images makes your content appear lazy and unprofessional. If each image is unique, the description should be too.

What The Alt Attribute In IMG Tags Is Really Used For

Technically speaking, the alt attribute in IMG tags serves as a fallback mechanism for images. It displays text when the image doesn’t load and helps screen readers describe the visual to users.

It’s not just a placeholder. It’s a functional element of your website’s code that serves users, supports search engines, and enhances the overall experience.

If you’re building a site from scratch or editing an existing one, be sure to include a relevant alt tag for every meaningful image. It’s one of the easiest improvements you can make to your content – and one that pays off across accessibility, user trust, and visibility.

So, what is an alt tag for an image? It’s much more than a technical label. It’s your chance to describe visual content in a way that serves everyone – visually impaired users, search engines, and people on slow connections.

Whether you’re managing a blog, running an online shop, or optimising a large content library, investing time in writing good alt attributes will improve accessibility, boost SEO, and show that your brand actually cares about quality and inclusion (which is key now more than ever).

If you’re not sure where to start or want to improve your current setup, now’s the time. A little effort goes a long way -and we’re here to help if you need it.