Image Alt Text That Actually Helps Your Rankings

Most websites get alt text wrong. Either every image has an empty alt="" tag, or someone stuffed every keyword they could think of into it. Both approaches waste one of the easiest on-page SEO signals you have. Here's how to write alt text that actually does something useful.

What Alt Text Is and Why It Matters

Alt text (short for "alternative text") is the text description you add to an image's alt attribute in HTML. It serves two purposes:

Accessibility

Screen readers read alt text aloud to visually impaired users. Without it, they hear nothing---or worse, the raw filename. This isn't optional. It's a legal requirement under ADA and WCAG guidelines.

SEO signal

Search engines can't see images the way humans do. Alt text is the primary way Google understands what an image contains and how it relates to your page content.

When you write good alt text, you help both audiences at once. When you skip it, you leave value on the table for both.

How Google Uses Alt Text

Google's image crawlers rely heavily on alt text to index images for Google Images search. But it goes beyond that. Alt text also helps Google understand the content and context of the page the image sits on.

Here's what Google specifically uses alt text for:

Google Images ranking. Alt text is the single strongest signal for determining where your image shows up in Google Images results. If you sell blue leather handbags and your product images have descriptive alt text, they can rank for those searches.
Page context. Alt text reinforces what your page is about. An image of a plumber fixing a sink with alt text "plumber repairing kitchen sink faucet in Portland home" tells Google your page is relevant to plumbing services in Portland.
Anchor text for image links. If an image is wrapped in a link, the alt text functions as anchor text. Google uses it to understand what the linked page is about---similar to how internal link anchor text signals relevance.

The Formula for Good Alt Text

Good alt text follows a simple formula: be descriptive, be specific, and include context. Think of it as answering the question: "If I couldn't see this image, what would I need to know?"

Describe what's in the image

Don't say "product photo." Say what the product actually is. Not "team photo" but "three engineers reviewing code on a monitor."

Be specific

Include relevant details like color, material, size, action, or location. "Shoes" is vague. "Red Nike Air Max 90 running shoes on white background" is useful.

Include page context naturally

If your page is about kitchen renovations in Austin, your image alt text can naturally include that context: "modern white kitchen with quartz countertops after renovation in Austin TX."

Keep it under 125 characters when possible. Screen readers typically cut off alt text beyond that length, and you don't need a novel. One clear, descriptive sentence is enough.

Common Mistakes That Hurt You

These are the alt text patterns we see on almost every site we audit. All of them either waste the signal or actively hurt your SEO.

Empty alt tags on content images

Leaving alt="" on meaningful images is the most common mistake. Google ignores the image entirely, and screen reader users get nothing.

Keyword stuffing

Writing alt text like "best plumber cheap plumber emergency plumber Portland plumber" is spam. Google knows it, and it can trigger manual penalties.

Starting with "image of" or "picture of"

Screen readers already announce the element as an image. Adding "image of" is redundant and wastes characters. Just describe what's in it.

Using the filename

Alt text like "IMG_4392.jpg" or "hero-banner-final-v2" tells no one anything. This is what happens when the alt attribute gets auto-filled from the filename, and it's completely useless.

Identical alt text on every image

If every product image on your category page says "product image," you're giving Google zero differentiation between them. Each image needs its own unique description.

Before and After Examples

Here are real-world examples of bad alt text rewritten the right way, for different types of images you'll find on a typical site.

Product photo

// Bad alt="product"

// Also bad alt="shoes sneakers running shoes buy shoes best shoes"

// Good alt="Navy blue New Balance 574 sneakers, side view on white background"

Team photo

// Bad alt="team"

// Good alt="Valrank engineering team working at a whiteboard in the Portland office"

Infographic or chart

// Bad alt="infographic"

// Good alt="Bar chart showing 65% of pages have missing alt text based on 2024 web accessibility study"

Screenshot

// Bad alt="screenshot"

// Good alt="Google Search Console performance report showing 12% increase in image clicks"

Decorative image

// Correct: empty alt for decorative images alt=""

When to Use Empty Alt Text

Not every image needs descriptive alt text. Decorative images that don't convey meaningful content should use an empty alt="" attribute. This tells screen readers to skip the image entirely, which is the correct behavior.

Use empty alt text for:

Background patterns and textures. Dot grids, gradients, decorative dividers---anything that's purely visual styling.
Icons that already have a text label next to them. If the icon sits beside text that says "Email us," the icon doesn't need its own alt text.
Spacer images or decorative borders. These are layout elements, not content.

The key distinction: if removing the image would cause the user to miss information, it needs alt text. If removing it changes nothing about the meaning of the page, use alt="".

Important: an empty alt="" is not the same as a missing alt attribute. Omitting the alt attribute entirely is an accessibility error. Including it but leaving it empty is a deliberate, valid choice.

How to Audit Your Site

You probably have missing or bad alt text right now. Here are three ways to find it, from fastest to most thorough.

Chrome DevTools (5 minutes)

Open any page, right-click an image, and select "Inspect." Look at the <img> tag in the Elements panel. Check if the alt attribute exists and whether the value is meaningful. Quick spot check, but manual.

Lighthouse audit (10 minutes)

Open DevTools, go to the Lighthouse tab, and run an accessibility audit. It flags images with missing alt attributes automatically. It won't tell you if the alt text is good, but it catches missing ones.

Screaming Frog (full site crawl)

Crawl your entire site with Screaming Frog SEO Spider. Go to the Images tab and filter by "Missing Alt Text" or "Alt Text Over 100 Characters." This gives you a complete list of every image that needs attention across your whole site.

For most sites, start with Lighthouse to get the quick wins, then do a full Screaming Frog crawl to catch everything. Prioritize images on your highest-traffic pages first. And while you're reviewing on-page elements, make sure your title tags are optimized and your heading structure is correct too.

Quick Checklist

Alt Text Checklist

✓Every content image has a descriptive, unique alt attribute
✓Alt text describes what's in the image, not just what the image is
✓No keyword stuffing---one or two relevant terms at most, woven in naturally
✓Alt text doesn't start with "image of" or "picture of"
✓Decorative images use alt="" (empty, not missing)
✓Alt text is under 125 characters
✓Image links use alt text that describes the link destination, not the image itself
✓No auto-generated filenames used as alt text (no "IMG_4392" or "hero-v2-final")

Alt text isn't glamorous, and it's never going to be the thing that moves you from page five to page one. But it's a genuine ranking signal that most sites ignore completely. Fix it once, and every image on your site starts working for you instead of sitting there doing nothing.