Alt text — short for alternative text — is a text description supplied through an image’s alt attribute in HTML.
Alt text — short for alternative text — is a text description supplied through an image’s alt attribute in HTML. It communicates the purpose and essential information of an image when that image cannot be seen.
Screen readers announce alt text aloud for users who are blind or have low vision. Browsers display alt text in place of an image if the image file fails to load. Search engines read alt text to understand what an image depicts and how it relates to the surrounding page content.
The alt attribute has been part of the HTML specification since HTML 2.0 (1995). What changed over time is not its technical function but the quality standards around it — modern accessibility guidelines like WCAG 2.2 and Section 508 require alt text that conveys meaning, not just a label.
An image tag with alt text follows this structure:
<img src="golden-retriever-beach.jpg" alt="Golden retriever running on a sandy beach at sunset">
src attribute points to the image file location. The alt attribute holds the text description.No — though the terms are often used interchangeably in everyday conversation. “Alt tag” is a colloquialism. The correct technical term is alt attribute, because alt is an attribute of the <img> element, not a standalone HTML tag. In practice, “alt text,” “alt attribute,” and “alternative text” all refer to the same concept.
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Alt text serves three distinct audiences, each with different needs.
Many use screen readers — software that converts on-screen content to speech or braille.
This is not a nice-to-have; it is a functional requirement under the Web Content Accessibility Guidelines (WCAG) 2.2, specifically Success Criterion 1.1.1 (Non-text Content).
Screen reader users rely on alt text to navigate product pages, understand infographics, identify buttons, and grasp the full meaning of a page. Missing or poorly written alt text excludes these users from the conversation entirely.
Images break. A slow connection, a server error, a deleted file, an email client that blocks images by default — all of these are common. When an image does not load and no alt text is present, users see either nothing or a cryptic file name.
Alt text provides a fallback that preserves meaning. In email marketing — where image blocking is widespread — alt text often determines whether a recipient understands the message at all. For affiliate marketers sending promotional emails, alt text on product images can mean the difference between a click and a delete.
Search engines use alt text alongside file names, surrounding copy, and page structure to index images. Google’s own documentation confirms that alt text helps the search engine understand what an image shows and how it relates to the page topic.
Images with descriptive, accurate alt text are more likely to appear in Google Image Search results — a channel that drives traffic independently of standard web search. For e-commerce and affiliate sites, image search can be a meaningful traffic source when product images carry appropriate alt text.
Yes — with a caveat. AI systems increasingly use computer vision to analyze images directly. However, when an AI model processes a page primarily through its text and HTML (as search crawlers and some content-indexing tools do), the alt text provides an explicit, author-written signal about what the image means in context. This is particularly relevant as AI-powered search features — such as Google’s AI Overviews — synthesize page content to answer user queries.
The decision to write alt text depends on the image’s purpose. The W3C Web Accessibility Initiative categorizes images into several types, each with different alt-text requirements.
Images that convey information relevant to the page need descriptive alt text. Ask: If this image disappeared, would the reader lose meaningful content? If yes, write alt text that communicates the information the image provides.
Functional images initiate actions — they appear inside buttons, links, or other interactive elements. Their alt text should describe the action, not the image itself.
Example: A magnifying-glass icon inside a search button needs alt="Search", not alt="Magnifying glass icon".
For functional images, the user needs to know what happens when they click — not what the icon looks like.
Whenever possible, text should be real HTML text, not embedded in an image. When images of text are unavoidable (banners, promotional graphics, some social-media templates), the alt text should reproduce the exact text shown in the image.
Example: A promotional banner reading “20% Off All Plans — Use Code SUMMER20” should have alt text containing those exact words.
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Decorative images serve no informational or functional purpose — they exist purely for visual ambiance. Background patterns, generic stock photos used as section dividers, and purely ornamental icons fall into this category.
For decorative images, use an empty alt attribute: alt="". This is also called null alt text.
This is the correct behavior; announcing decorative images adds noise without adding meaning.
Critical detail: The alt attribute must still be present, just empty. Omitting the alt attribute entirely (<img src="decorative.jpg">) forces screen readers to read the file name, creating a worse experience than null alt text.
When an image repeats information already present in adjacent text, adding alt text creates duplication. For example, if a product card shows an image of a “Wireless Bluetooth Headphones” next to a heading that says “Wireless Bluetooth Headphones,” the alt text should be empty — alt="" — because the information is already available to screen reader users through the heading.
The difference between adequate alt text and useless alt text often comes down to a few basic principles.
Describe the information the image conveys, not every visual detail. A photograph of a person hiking does not need the color of their shoelaces — it needs the action, context, and any details relevant to the surrounding content.
Most effective alt text fits within 125 characters. Screen readers pause at punctuation, so long, unbroken alt text becomes an audio wall. Siteimprove recommends keeping alt text under roughly 100 characters whenever possible.
The same image can need different alt text depending on where it appears. A photo of a laptop on a desk might need alt text describing the laptop model on a product page, or alt text describing a remote-work scene on a blog about productivity.
Always write alt text for the image’s role on the specific page, not for the image in isolation.
Alt text exists for accessibility first. Use relevant terms only when they naturally describe the image.
Screen readers already announce an image as an image.
Capitalize the first letter. End sentences with a period. Screen readers use punctuation to determine pacing and intonation. Grammatical alt text sounds more natural and is easier to understand.
When the alt attribute is completely absent from an <img> tag, behavior varies:
DSC00472.jpg.An image with a missing alt attribute is fundamentally different from one with an empty alt="". The first creates confusion; the second is a deliberate choice that tells assistive technology to skip the image. Every <img> tag on a page should have an alt attribute — whether populated or empty.
Most CMS platforms — WordPress, HubSpot, Shopify, and others — include an alt text field in the image upload or media library interface.
In WordPress, when you select an image in the block editor or media library, the “Alternative Text” field appears in the right-hand settings panel. Enter your description and save. The CMS adds the alt attribute to the HTML automatically.
Add the alt attribute directly inside the <img> tag:
<img src="affiliate-dashboard.jpg" alt="Post Affiliate Pro dashboard showing monthly commission summary">
alt attribute can appear anywhere within the <img> tag, though placing it after src is conventional.Most social platforms provide an alt-text option when composing a post with an image:
Always replace auto-generated alt text with a human-written description. AI-generated alt text tends toward generic labels — “dog, indoor, person” — that miss the image’s purpose and context.
Alt text plays a specific and often overlooked role in affiliate marketing workflows, affecting advertisers, publishers, and program managers alike.
When you provide banners, product images, and promotional creatives to your affiliates, those images rarely ship with alt text. Affiliates who receive an image file through an affiliate dashboard may not know what to write — and many will leave the alt attribute blank or missing.
Program managers who include suggested alt text alongside each creative in the affiliate portal remove that friction.
Product review posts and comparison articles rely heavily on screenshots, product photos, and comparison tables rendered as images. Each of those images needs alt text that serves both the reader and the search engine.
When readers using screen readers encounter that alt text, they receive the same information a sighted reader gets from the screenshot. When search engines index that alt text, the image can surface in relevant queries about affiliate commission settings.
Product images with accurate, descriptive alt text can rank in Google Image Search for long-tail queries. That image click leads to the page — and potentially to a signup.
This is not a substitute for written content and standard SEO. It is an additional, low-effort channel that works only when alt text is consistently applied.
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