Guide · Updated October 2026

What Is Alt Text and How Do I Write It for My Website?

Alt text describes images for screen readers and search engines. Learn what it is, why it matters for accessibility and SEO, and how to write good alt text.

Short answer: Alt text (alternative text) is a short written description attached to an image in your website's code. Screen readers read it aloud to blind and partially sighted visitors, it appears if an image fails to load, and search engines use it to understand your images. Good alt text describes what the image shows and why it matters, in one short sentence.

What it looks like in code

Alt text sits in the alt attribute of an image tag, like this: <img src="kitchen.webp" alt="Newly fitted white kitchen with oak worktops">. On most platforms you never touch the code; there is an "alt text" or "image description" box when you upload or edit an image.

Three reasons it matters

Accessibility

People using screen readers cannot see your photos. Without alt text, they may hear a file name like "IMG underscore 2041" or nothing at all. With it, they get the same information as sighted visitors. Alt text is a core part of the WCAG accessibility guidelines.

SEO

Search engines cannot fully "see" images the way people do. Alt text helps them understand what an image is about, which supports image search results and gives extra context for the page.

Fallback

If an image fails to load on a slow connection, the alt text appears in its place, so the page still makes sense.

How to write good alt text

Describe what matters: what would you tell someone on the phone about this image?
Be concise: aim for one short sentence. Around 125 characters or fewer is a common guideline because some screen readers handle long text awkwardly.
Skip "image of" or "picture of": screen readers already announce it is an image.
Add context naturally: if location or service is relevant, include it, but only if it is true and useful.
Do not stuff keywords: alt text written for robots reads terribly to people and can look spammy to search engines.

Accessible, search-friendly sites with every image described properly. That is the SiteDrum standard.

SiteDrum builds fast, mobile-first websites from $99 setup and $15 a month, with hosting, security, Google setup and support included. Already have a site that is slow or broken? Try Website Rescue or run our free speed test.

Before and after examples

Weak: alt="image1"
Better: alt="Electrician fitting a new consumer unit in a home"
Weak: alt="plumber plumber London best plumber cheap plumber"
Better: alt="Plumber repairing a leaking pipe under a kitchen sink in London"
Weak: alt="team"
Better: alt="Sarah and James, salon owners, standing at the reception desk"

Special cases

Decorative images

Background patterns, dividers and purely decorative graphics should have empty alt text: alt="". That tells screen readers to skip them. Do not leave the attribute out entirely, as some screen readers then read the file name.

Logos

Use your business name, for example alt="Greenway Landscaping". If the logo links to your homepage, "Greenway Landscaping home" works well.

Images containing text

If an image includes words, such as an offer banner, the alt text should include those words. Better still, put important text in real HTML, not inside images.

Charts and infographics

Give a short summary in the alt text and explain the details in the surrounding text.

Fixing alt text across an existing site

Start with your most important pages: homepage, service pages and contact page. Most CMS media libraries let you edit alt text for each image. A website crawler or accessibility checker can list every image missing alt text. If that list is long, our Website Rescue service can work through it for you.

The bottom line

Alt text is a short description that makes images accessible, helps search engines and keeps pages readable when images fail. Describe what matters in one natural sentence, leave decorative images empty, and never stuff keywords. It is quick to do and helps every visitor.

Frequently asked questions

What is alt text used for?

It describes images for screen reader users, displays if an image fails to load, and helps search engines understand what images show.

How long should alt text be?

Usually one short sentence, around 125 characters or fewer, describing what is important about the image.

Should every image have alt text?

Every meaningful image should. Purely decorative images should have empty alt text so screen readers skip them.

Does alt text help SEO?

Yes. It helps search engines understand images and can support visibility in image search, as long as it is descriptive rather than keyword-stuffed.

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