What is Alt Text (Alternative Text)?
Also known as: Alt attribute, Alt tag, Image description
What is alt text?
Alt text (short for alternative text) is a written description of an image, added inside the HTML alt attribute of an <img> tag.
<img src="orange-tabby-cat.jpg" alt="Orange tabby cat sleeping on a windowsill in afternoon sunlight">The text never appears on the rendered page when the image loads correctly. It surfaces in three situations: a screen reader reads it aloud, the image fails to load, or a search engine crawler indexes the page.
Three audiences read alt text:
- Screen reader users. Roughly 2 percent of web users rely on assistive technology, per the WebAIM Screen Reader Survey #10.
- Search engines. Google, Bing, and AI crawlers use alt text as a primary signal for image classification.
- Anyone on a slow connection. When images fail, the alt text is the fallback content shown in the browser.
Why does alt text matter?
Alt text matters because it is the single piece of code that serves accessibility, SEO, and resilience at the same time. Skip it and you lose users, lose image search traffic, and lose the page's fallback experience. Three concrete reasons it matters:
Accessibility (the legal one)
The W3C Web Content Accessibility Guidelines (WCAG) 2.1, Success Criterion 1.1.1, requires a text alternative for every non-text content element. This is a Level A requirement, the minimum bar for public websites. ADA lawsuits in the US, EAA enforcement in the EU, and AODA in Canada all cite missing alt text as a top-three accessibility violation in automated audits.
Image SEO
Google Image Search drives meaningful visual traffic to e-commerce and content sites. Per Google's Image SEO best practices, alt text is one of the main signals Google uses to understand what an image shows. Without it, a product image might rank nowhere. With it, the same image can rank for the exact descriptive terms a buyer types. Pair it with structured data and the image becomes eligible for richer Image Search treatments.
Email image fallback
Most email clients block remote images by default until the recipient clicks "show images." Alt text is what the recipient sees in the meantime. A promotional email with empty alt attributes shows blank rectangles. The same email with descriptive alt text reads like a usable message even before images load.
How do you write good alt text?
Good alt text is specific, concise, and describes the image's purpose in context. Bad alt text is vague, repetitive, or stuffs keywords. The easiest test: read the page aloud with the alt text in place of every image. Does it still make sense?
| Bad | Good |
|---|---|
alt="image" | alt="Coinis dashboard showing 12 generated ad creatives for a skincare brand" |
alt="shoes" | alt="Red Nike Pegasus 40 running shoes, side view" |
alt="DSC_4521.jpg" | alt="Bar chart of monthly organic traffic, growing from 4k to 18k visits" |
alt="ad creative ai ad maker ad generator best ad tool" | alt="AI-generated Facebook ad showing a coffee cup and the headline 'Brewed bold'" |
alt="logo" (in header) | alt="Coinis" (or empty if a text logo sits next to it) |
Three rules cover most cases:
- Describe what the image shows and why it is there. Context beats raw description. A graph image needs the takeaway, not just "graph."
- Don't start with "image of" or "picture of." Screen readers already announce the element as an image. The phrase is redundant.
- Match the surrounding copy. If the body already explains the chart, the alt text can be short. If the image carries information not in the text, the alt text must carry it.
Alt text vs title attribute vs caption
These three get confused often. They serve different jobs.
- Alt text (
altattribute). The accessible, machine-readable description. Required for non-decorative images. Read by screen readers. Indexed by Google as part of image SEO. - Title attribute (
title). A tooltip shown on mouse hover. Inconsistently exposed by screen readers. Generally skip it. - Caption (
<figcaption>inside<figure>). Visible text shown to all users below or beside the image. Adds context everyone sees. Captions and alt text can coexist. They should not duplicate each other.
The pattern that works: alt text describes the image, caption explains its meaning, and the title attribute stays unused.
Decorative images and the empty alt attribute
Not every image needs a description. Decorative images are visuals that add no information beyond aesthetics: background textures, divider flourishes, icons that sit next to a text label that already says the same thing.
For these, use an empty alt attribute:
<img src="divider-line.svg" alt="">The empty alt="" tells screen readers to skip the image. The reader moves to the next element without saying anything. This is the correct behavior.
What you must not do is omit the attribute entirely. With no alt at all, many screen readers fall back to reading the file name. Users hear "decorative slash divider line dot s v g" announced for every spacer in your design system.
The WebAIM guide to alternative text is the canonical reference. Read it once, then default to: meaningful image gets descriptive alt, decorative image gets alt="".
Real-world example: alt text on an e-commerce product page
A direct-to-consumer running shoe brand has 240 product pages. Each page has 5 images: hero, side angle, sole, lifestyle, size chart.
Before the alt text audit:
- 70 percent of images use
alt="product"or empty filename-only alt. - Google Image Search delivers 1,200 monthly visits across the catalog.
- Lighthouse accessibility score: 78.
The team rewrites every alt attribute. Hero images get the full product name plus colorway plus angle. Lifestyle shots describe the scene. Size charts get the measurement table summary. Size 60 minutes per page, 240 pages, two writers, two weeks.
Three months after the rewrite:
- Google Image Search delivers 4,800 monthly visits, a 4x lift.
- Image-driven sessions convert at 2.1 percent, beating the site average of 1.4 percent.
- Lighthouse accessibility score: 96.
- One ADA demand letter that arrived during the project gets resolved without litigation.
The work cost roughly 80 hours. The recovered traffic alone paid for it inside six weeks.
Alt text in 2026: multimodal AI search
Alt text matters more now than it did three years ago. Two shifts caused it.
First, Google's Multisearch and AI Overviews increasingly pull images directly into answers. The image's surrounding context, including alt text, decides whether your image gets cited or your competitor's does.
Second, ChatGPT, Claude, Perplexity, and Gemini all crawl public web content for training and retrieval. Their multimodal pipelines read alt text alongside image embeddings to label what an image contains. A page with rich, accurate alt text gets correctly classified. A page without it gets guessed at, often wrong.
The practical implication for a 2026 content team: treat alt text as production copy. Have a writer review it. Audit it quarterly. Include it in the same QA pass you run on titles and meta descriptions. The cost is small. The compounding return across accessibility compliance, SEO, email rendering, and AI citation is large.
In practice, every image that ships on a Coinis-generated landing page or ad creative includes auto-drafted alt text based on the source product feed and image content, which the marketer can review and edit before publish. The default is descriptive. The default is reviewable. The default is never empty.
Related terms
Frequently asked questions
What is the difference between alt text and a title attribute?
Alt text describes the image for users who cannot see it. The title attribute shows a tooltip on hover for sighted mouse users. Screen readers usually ignore title attributes. Search engines weight alt text far more heavily. Always write alt text. Skip the title attribute unless you have a specific reason.
How long should alt text be?
Aim for 8 to 15 words. Most screen readers cut off around 125 characters. Google has no hard limit but rewards specific, descriptive phrasing. If a single image needs more than 15 words to explain, the longer description belongs in a caption or surrounding body text, not the alt attribute.
Do decorative images need alt text?
No. Purely decorative images (background patterns, divider lines, icons paired with visible text labels) should use an empty alt attribute: alt="". This tells screen readers to skip the image entirely. Omitting the alt attribute is worse. Screen readers then read the file name aloud, which is almost always useless.
Does alt text affect SEO rankings?
Yes, for image search. Google's Image SEO best practices confirm alt text is one of the primary signals used to understand image content. It also boosts page-level relevance for the keywords described, and it counts toward the anchor text when an image is linked.
What happens if I stuff keywords into alt text?
Google's image guidelines explicitly warn against keyword stuffing. Pages that pack alt attributes with keyword lists like alt="running shoes red running shoes nike running shoes" get treated as spam. Write the alt text for a person who cannot see the image. Natural keyword inclusion happens on its own.