Alt tag / Image alt text

What Is Image Alt Text?

Image alt text is a short written description of an image that appears when the image can’t be displayed. It ensures accessibility for users and helps search engines understand your content.

You may also hear it called “alt tags,” “alt attributes,” or “image tags.” While the technical name in SEO tools like Semrush is “image alt attribute,” the function is the same: to describe an image in words. When an image fails to load—due to slow internet, disabled images, or assistive technology—this text is shown in its place.

Alt text plays a vital role for people with visual impairments, including those who are blind or color blind, allowing screen readers to communicate what’s in an image. It also improves user experience for people with slow connections or those who disable images for focus and readability.

What it’s not: alt text is not the text inside the image itself. If an image contains visible text, you may incorporate that into the alt description—but alt text should be written separately, not embedded in the image.

Why Is Image Alt Text Important for SEO?

Image alt text helps Google understand what an image depicts, which can improve your site’s accessibility and search rankings.

From Google’s perspective, a quality search result must work for everyone—whether they have a visual impairment, a slow connection, or a minimal-browsing preference. Pages that lack proper alt text create a poorer user experience, which can indirectly harm rankings.

Google uses alt text to index images in Google Images, providing another potential traffic source. When written naturally and accurately, it can help relevant searches find your content. But keyword stuffing—forcing unrelated or repetitive keywords into alt tags—can send spam signals to search engines and damage trust.

How Should You Write Image Alt Text?

Write image alt text as if you’re saying, “This is a picture of…” and then finish the sentence.

This simple mental model keeps descriptions natural and prevents keyword stuffing. For example:

• Poor: “New York wedding photographer” repeated on every photo

• Good: “Bride and groom cutting wedding cake”

Alt text should be specific enough for clarity but concise enough to be understood at a glance. Long-winded descriptions (e.g., three or four sentences) overwhelm the reader and defeat the purpose of having an image.

While older SEO advice recommended keeping alt text to 3–5 words, modern best practices lean toward short phrases or one brief sentence, especially as AI tools increasingly suggest longer, more descriptive tags. The key is balance: be clear, accurate, and quick to read.

What Should You Avoid in Image Alt Text?

Avoid keyword stuffing, vague labels, and overly long descriptions when writing alt text.

Search engines can detect when the same keyword is repeated unnecessarily across images, and this can be interpreted as spam. Similarly, labels like “image123.jpg” or “photo” provide no value. And while detail is good, four-sentence alt text is overkill—no image should require a paragraph to explain.

Your goal is clarity for both human readers and search engines. If the description doesn’t help someone visualize the image without seeing it, rewrite it.

Before & After Optimization Table

Example Context	Poor Example	Optimized Example
Wedding reception photo	“New York wedding photographer”	“Bride and groom dancing under string lights”
Product image of red sneakers	“Shoes”	“Pair of red running sneakers on wooden floor”
Infographic with statistics	“Chart”	“Bar chart showing 10% growth in online sales”

How Long Should Image Alt Text Be?

Keep alt text short—ideally under 125 characters—to make it quick to read and compatible with screen readers.

This limit isn’t a strict SEO rule, but a practical guideline for accessibility. Screen readers often cut off descriptions after about 125 characters, so concise writing ensures your message is delivered in full.

If you find yourself writing more than a sentence, consider whether the detail belongs in a caption or the body text instead. Alt text should be a visual summary, not an essay.

What Happens If You Don’t Use Alt Text?

Without alt text, your images are invisible to users who can’t see them and to search engines that can’t interpret them.

For accessibility, this means blind or visually impaired users may miss important context, which could make your site less compliant with accessibility standards. For SEO, it means lost opportunities to appear in Google Images and reduced clarity for search engines crawling your site.

In short, skipping alt text hurts both user experience and discoverability.

Bottom Line

Image alt text is more than an SEO checkbox—it’s a critical part of web accessibility and user experience. Keep it descriptive but concise, avoid keyword stuffing, and think like a human describing an image to another human. Done right, it will help your site serve more users and perform better in search.