How to Write Alt Text: SEO Best Practices

Images make website content easier to understand and more engaging, but not everyone can see or load them. Knowing how to write alt text helps screen reader users understand image content and gives search engines additional context.

Alt text is not a place to stuff keywords or describe every detail in an image. This article explains what alternative text is, when to use it, how to create effective descriptions, and how to tell useful examples from less suitable ones.

What Is Alt Text and What Is It For?

Alt text, or alternative text, is a written description associated with an image on a web page. If an image does not display, the browser may use this text in its place. Screen readers also read alt text so people who are blind or have low vision can access the information conveyed by the image.

Content specialist discussing how to write alt text and improve image accessibility on a website — Writing alt text conveys the meaning of images to screen reader users and provides additional context for search engines.

For SEO, alt text gives search engines context to understand what an image contains and how it relates to the page. This can help images appear in relevant image search results. However, alt text is only one part of image optimization; it does not guarantee rankings or replace useful content, site structure, or loading speed.

Alt text is different from an image caption. Captions usually appear directly below an image and provide information for all readers. Alt text is typically set in the HTML, such as in an image element’s alt attribute. If an image has both a caption and alt text, each should serve its own purpose without needlessly repeating the same wording.

Principles for Writing Clear, Useful Alt Text

1. Describe the Important Content or Function

Start by asking: What does a reader need to know if they cannot see the image? For an illustrative image, describe its main content. For an image that acts as a button or link, describe its function. There is no need to list every color, layout detail, or object unless it helps users understand the page.

Marketing employee identifying essential details when writing concise, context-appropriate alt text — When writing alt text, prioritize the image’s important content or function and describe it naturally in the context of the page.

For example, an image of a coffee machine on a product page may need to name the product and mention an important feature. But a decorative image next to a paragraph that already conveys the same idea in full usually does not need a lengthy description.

2. Keep It Concise, Specific, and Relevant

Put the most important information first and use natural wording. The right length depends on the image, but a short sentence is usually easier to follow than a long description. There is no fixed character count that works in every case; prioritize clarity instead of aiming for a specific length or adding as many keywords as possible.

The page context also shapes the description. The same image may need different alt text on a staff profile page, an article about a manufacturing process, or a product category page. Describe what matters in the specific context, not just what is visible.

3. Use Keywords Naturally; Don’t Stuff Them

If a relevant keyword directly relates to the image and makes the description more accurate, you can include it naturally. For example, an image illustrating a specific product may name that product. In contrast, adding phrases like “cheap,” “trusted,” or “best” to an image that does not show those qualities makes the description less useful.

Think of write alt text as describing an image for users first, rather than as a way to add SEO keywords. If a sentence sounds awkward when read aloud or repeats a phrase several times, rewrite it.

4. Avoid Unnecessary Openings

Usually, there is no need to start with “image of,” “photo of,” or “illustration of.” Assistive technology may already announce that the item is an image, so these opening phrases can make the description longer without adding value. Still, always prioritize clarity and follow the conventions of the platform or content management system you use.

Good and Less Effective Alt Text Examples

Comparing examples is a quick way to spot the difference between a useful description and one that merely repeats keywords. The examples below are illustrative; adapt them to the actual image and page content.

Marketing team comparing appropriate ways to write alt text for website product images — Good alt text focuses on accurate, useful details instead of repeating keywords or using a generic description.

Quarterly revenue chart: Less effective: “chart, revenue, business, report.” Better: “Revenue rose from Q1 through Q3, then dipped slightly in Q4.” If users need full access to the chart data, include it in the page content or a separate table rather than relying entirely on alt text.
Product image: Less effective: “buy bottle water bottle beautiful bottle good price.” Better: “Blue LilyTech insulated bottle with a flip-top lid and carry handle.” Mention the brand, color, or features only when they are accurate and useful.
Image of an employee advising a customer: Less effective: “photo of a woman.” Better, in an article about consulting services: “Consultant discussing a marketing plan with a client at a desk.” This describes a relevant activity rather than stopping at a generic characteristic.
Image that links to the contact page: Less effective: “image of a phone.” Better: “Contact the consulting team.” When an image is the only content in a link, its alt text should help users understand the destination or action.
Decorative image next to complete content: Less effective: a lengthy description of an informationally irrelevant background pattern. Better: use empty alt text (alt="") for purely decorative images so screen readers can skip unnecessary content.

These examples show that good alt text does not have to be long. It should accurately describe the image, serve its purpose, and avoid creating noise for users. Do not claim information that cannot be verified from the image alone, such as a person’s name, location, or product feature not stated in the content.

How to Handle Special Image Types

Images Containing Text or Important Information

If an image contains information readers need, the alt text should convey the main point of that text. For an image with multiple sentences, a data table, or a complex chart, do not try to squeeze everything into one alt text sentence. Provide a transcript, detailed description, or data table on the page, then use concise alt text to explain the image’s purpose.

Specialist reviewing how to write alt text for product images, charts, and decorative images — For complex, linked, or decorative images, write alt text that matches the image’s function and provide an explanation when needed.

Product Images in Online Stores

Describe attributes that help distinguish the product, such as its name, type, color, or viewing angle when relevant. Do not repeat the entire product title if it adds no information. If there are multiple images of the same product, describe what differs in each one, such as the back view, material details, or how the product is used, rather than using the same sentence for all of them.

Images in Links and Buttons

When an image is the only clickable element, its alt text should convey the function or destination. If an image is purely decorative and sits beside a link that already has a clear text label, you can use empty alt text to avoid repetition. Assess how the element is built on the page rather than deciding based only on the image file itself.

Decorative Images

Not every image needs a description. Patterns, borders, or backgrounds that provide no additional information generally use empty alt text. Empty alt text is different from leaving out the alt attribute: the attribute is present, but its empty value tells assistive technology that the image can be skipped.

A Workflow and Checklist for Reviewing Alt Text

To apply alt text consistently across a website, content writers and design and development teams can use this simple workflow:

Website team reviewing the alt text writing process and image quality before publication — An alt text checklist helps teams review accuracy, clarity, and how decorative images are handled before publishing.

Identify the image’s role: Does it provide information, function as a link or button, or serve only as decoration?
Choose the information to convey: If users cannot see the image, what do they need to know to understand the content or take action?
Write a specific description: Use natural language, put important information first, and remove irrelevant details.
Check the context: Does the alt text add to the written content, or merely repeat the caption and nearby text?
Verify accuracy: Check that product names, colors, data, and activities match the image.
Review the assistive experience: Use a screen reader or checking tool to find images missing alt text, redundant descriptions, and decorative images that have not been handled appropriately.

Quick checklist before publishing: Does the alt text reflect the image’s purpose? Is it concise and easy to understand when heard aloud? Are keywords used naturally and accurately? Are decorative images handled so they can be skipped? Is there an alternative explanation on the page for complex content? If the answers are clear, you have a strong foundation for consistent implementation.

Businesses with many product pages or articles should create internal guidelines so content editors know how to describe each type of image. LilyTech can help businesses review website content, page structure, and user experience elements, including how alternative text is managed in the publishing workflow.

Conclusion: Write Alt Text That Helps Users and SEO

The core principle of writing alt text is to accurately describe an image’s content or function in the context of the page, without stuffing it with keywords. Distinguish between informational, linked, and decorative images. For charts or complex content, provide an accessible explanation rather than relying on a single description.

When building a publishing workflow, write alt text should be a content quality and accessibility check, not an SEO task done just for show. If your business needs advice on improving its website and digital content experience, contact LilyTech to discuss your needs and the right approach.