Alt Text Is Not an SEO Ranking Factor for Web Search: What It Actually Does and How to Write It Properly

Most SEO advice about alt text frames it as a ranking signal you need to optimize. Write descriptive alt text, it says, include your keywords, and your page will rank better. That framing is half right and half wrong in ways that matter. Google's Search Advocate John Mueller has stated directly that alt text doesn't add value to a page when it comes to ranking in web search. It's applied to the image, and if someone searches for the image, Google can use it to better understand the image. But the webpage in text web search doesn't rank better because it has an image. That distinction, web search versus image search, is the one most alt text guides quietly skip over, and it changes how you should think about the whole task.

What Alt Text Actually Does in a Browser

Before the SEO conversation, it helps to understand what the attribute was designed to do. The alt attribute is an HTML specification that predates modern search engines. Its original purpose was to provide a text alternative for an image in contexts where the image couldn't be displayed, whether because a browser had images disabled, a slow connection interrupted the load, or a user was accessing the page through a screen reader. When a screen reader encounters an image with no alt attribute, it typically announces "image" and nothing else. That's not useful. A well-written alt attribute gives visually impaired users the same information a sighted user gets from looking at the image.

Mueller confirmed in a Google Search Central office hours session that alt text is essentially shown when images are turned off in most browsers, and is counted as part of the on-page text. That last part matters for how Google indexes your page, but it's not the ranking signal it's often made out to be for general web search.

The Two Things Alt Text Actually Influences

Image search visibility is where alt text has clear, documented SEO value. Mueller has stated that if you want your images to rank in Google Image search, it is extremely helpful to Google if you add alt text. If your images are a meaningful traffic source, say you run a recipe site, a photography portfolio, or an e-commerce store where people frequently search for products by appearance, then writing descriptive alt text for those images directly affects whether they appear in image search results. For a site where images are purely decorative or functional, the image search benefit is minimal.

Accessibility is the more important reason in our view, and it's the one that gets the least attention in SEO-focused alt text guides. Mueller has been clear that alt text is not primarily an SEO tool. Its purpose is to improve accessibility and make the internet more inclusive. Screen reader software used by blind and low-vision users reads alt text aloud. JAWS, one of the most widely used screen readers, processes alt text in chunks up to 125 characters. An alt attribute that says "image" or is left empty tells a screen reader user nothing. One that says "Dalmatian puppy playing fetch in a backyard" tells them exactly what a sighted user sees.

The Context Problem That AI-Generated Alt Text Can't Solve

This is the most practically useful thing Mueller has said about alt text, and it's underreported in most summaries of his guidance. In a Reddit discussion picked up by uSERP and Stan Ventures, Mueller's advice emphasized not using alt text only to describe what's in the image, but as an opportunity to provide important context about how the image relates to the webpage's content. His example illustrates this clearly: "a hotel with a stunning beach and coral reefs" versus "a beach with an oil spill" could both be accurate visual descriptions of similar images, but they convey completely different meanings depending on the page they're on.

This is also why Mueller cautioned against relying on AI to generate alt text automatically. While AI can identify what's in an image, it can't consistently capture its context or purpose on that specific page. A generic alt text like "photo of a beach" doesn't help users or search engines understand the image's relevance to the webpage. The context is something only the person who chose that image for that page actually knows.

What Good Alt Text Looks Like in Practice

The W3C, which maintains the web's accessibility standards, offers a useful test for writing alt text: imagine reading the page aloud over the phone to someone who can't see it. When you reach the image, what would you say to convey the same information a sighted reader gets from it? That's your alt text.

A few concrete contrasts illustrate the difference between useful and unhelpful. A product photo on an e-commerce page shouldn't use alt="product". It should describe the specific item: alt="Men's dark navy wool overcoat with double-breasted buttons". A chart showing quarterly revenue trends shouldn't use alt="chart". It should convey the chart's main finding: alt="Bar chart showing Q3 revenue of $4.2M, up 18% from Q2". A purely decorative divider line or background texture genuinely doesn't need alt text. The correct approach there is an empty alt attribute (alt=""), which tells screen readers to skip the image entirely rather than announcing it as an unlabeled graphic.

Mueller has also clarified the distinction between the alt attribute and the title attribute for linked images. The alt attribute should describe the image itself. The title attribute, when the image is a hyperlink, should describe what happens when you click it, such as "View a larger version of the image."

Where Keyword Placement in Alt Text Becomes a Problem

The SEO advice to "include your target keyword in alt text" isn't wrong in every situation, but it's frequently misapplied. If a keyword naturally describes what's in an image, using it is appropriate. If you're writing alt text specifically to insert a keyword that doesn't actually describe the image, that's a different matter. As Google's own guidance states, overloading images with keywords in an attempt to manipulate SEO can result in penalties, and the focus should be on a natural, user-focused experience. An image of a person using a laptop in a coffee shop shouldn't have an alt attribute stuffed with unrelated keywords. It should describe the image.

The distinction is simple even if it's not always practiced: write alt text for the user who can't see the image, not for the algorithm that crawls your page. The algorithm, as Mueller has explained repeatedly, is primarily using alt text to understand the image itself and its potential relevance to image search, not to determine how your text web search ranking should change.

Checking Your Own Pages

If you publish articles with images and you're not sure whether your alt text is in reasonable shape, the most direct method is inspecting your page's HTML. Right-click any image in your browser and select "Inspect" or "Inspect Element" to see the alt attribute value. An empty value means no alt text. A value of "image," the filename, or something generic means it was likely auto-filled rather than written. A specific, contextual description means it's doing its job.

For writing and editing articles where you'll be adding images, our Word Counter is useful for keeping individual alt text descriptions concise. The 125-character limit relevant to JAWS screen reader processing is a practical ceiling worth staying inside. Paste a draft description in and check the character count before adding it to your HTML.

The Practical Summary

Alt text matters. Just not primarily for the reason most SEO guides say it matters. Write it for accessibility first, for image search second, and don't think about it as a web search ranking lever at all. Describe what's in the image, add the context that connects it to the page, keep it specific and concise, and use an empty alt attribute for genuinely decorative images rather than leaving it out entirely. That's the actual guidance from the people at Google responsible for explaining how this works, and it's simpler than most of the SEO frameworks built around it.