Every image on your website carries information. For sighted users, that information arrives instantly. For users relying on screen readers — software that converts on-screen content into audio or Braille — images are silent unless you add alt text. Alt text accessibility is the bridge between your visual content and the millions of people who cannot see it. Without it, a significant portion of your audience experiences your site as a series of gaps and unknowns.
This guide explains how screen readers use alt text, what goes wrong when it is missing, and the seven concrete ways correct alt text transforms the experience for visually impaired users.
How screen readers use alt text
Screen readers such as JAWS, NVDA, VoiceOver (macOS and iOS), and TalkBack (Android) process your webpage HTML from top to bottom. When they reach an <img> element, they look for the alt attribute:
<img src="bar-chart.jpg" alt="Bar chart showing 40% increase in organic traffic after adding alt text">
The screen reader reads the alt text aloud — or outputs it to a Braille display — giving the user a description of the image in context. There is no AI interpretation, no guessing. Just whatever you write in that attribute.
The Web Content Accessibility Guidelines (WCAG 2.1) formalise this as Success Criterion 1.1.1 (Non-text Content), a Level A requirement — the minimum baseline every website should meet.
What happens when alt text is missing
Three things can go wrong when alt text is absent or poorly written:
1. Missing alt attribute entirely — Some screen readers read the image filename aloud: "IMG_20240315_142233.jpg". This is meaningless to the user and actively disruptive to the reading flow.
2. Empty alt attribute (alt="") on a meaningful image — The screen reader skips the image silently. This is correct for decorative images, but catastrophic for images that carry information.
3. Generic alt text (alt="image" or alt="photo") — The screen reader announces “image, image” — providing no information at all. Many WordPress themes and plugins that auto-fill alt text with the attachment title produce exactly this failure.
Each scenario leaves the screen reader user without context that sighted users absorb automatically.
See the most common alt text mistakes for the full breakdown of how each failure affects both accessibility and SEO.
The WCAG 1.1.1 requirement — and the legal risk
Alt text accessibility is not optional under WCAG 2.1 Success Criterion 1.1.1. Every non-decorative image must have a text alternative that serves the same purpose as the visual.
Beyond guidelines, this carries legal weight. In many jurisdictions — including the United States under the ADA and the EU under the European Accessibility Act — commercial websites are expected to meet WCAG 2.1 Level AA. Businesses have faced litigation for failing to provide accessible image descriptions. The risk is real and growing.
If your images lack alt text, you are not just missing an SEO signal. You are potentially excluding a meaningful portion of your audience from your content, and exposing yourself to compliance risk.
7 ways alt text improves accessibility for visually impaired users
1. Describes what an image shows
The most fundamental role of alt text accessibility: telling a screen reader user what is in the image. A product photo, a diagram, a screenshot — all are silent without alt text. A well-written description gives visually impaired users the same informational starting point as everyone else on the page.
2. Makes infographics and charts usable
Images that contain data — bar charts, pie graphs, infographics — are particularly critical. The visual communicates multiple data points at once. Your alt text must capture the key takeaway: alt="Bar chart: organic traffic up 40% after alt text audit, April 2025". A generic alt="chart" renders the entire data point inaccessible.
3. Provides labels for linked images
When an image is wrapped in a link, the alt text becomes the link label. Without it, screen readers announce "link, image" — giving the user no indication of where the link leads. Linked images with empty or missing alt text are one of the most common and severe alt text accessibility failures on commercial websites.
<!-- Wrong -->
<a href="/pricing/"><img src="buy-now.png" alt=""></a>
<!-- Correct -->
<a href="/pricing/"><img src="buy-now.png" alt="View Image Alt Text Pro pricing"></a>
4. Describes actionable image buttons
Image buttons — an <img> inside a <button>, or an <input type="image"> — require alt text that describes the action, not the visual. alt="Submit" or alt="Search" is correct. alt="magnifying glass icon" is not. It describes the image rather than what pressing it does.
5. Preserves meaning on slow or failed loads
When an image fails to load — on a slow mobile connection, in a low-bandwidth environment, or when images are disabled by the user — the alt text appears in the browser in place of the image. Screen reader users are not the only beneficiaries. Every user on a broken or slow-loading page receives the alt text as a fallback.
6. Supports low-vision and high-contrast users
Not all users of accessibility tools are fully blind. Many users have low vision and use screen magnification combined with a screen reader. Accurate alt text lets them supplement what they can partially see with a clear written description — particularly useful when an image is magnified to the point where context is lost.
7. Reduces cognitive load during screen reader navigation
Screen reader users navigate pages differently from sighted users — often jumping between headings, links, and landmarks. Descriptive alt text reduces the cognitive effort required to reconstruct what a page is communicating. Without it, users are forced to infer meaning from surrounding context alone. Clear alt text accessibility practice keeps the reading experience cohesive and efficient.
Decorative images: when to leave alt text empty
Not every image needs descriptive alt text. Purely decorative images — visual flourishes that add no content meaning — should have an explicitly empty alt attribute: alt="". This signals to screen readers to skip the image entirely, rather than reading a filename or announcing “image.”
How to decide: if removing the image would cause a reader to miss information, it needs alt text. If removing it would only affect visual appearance, use alt="".
How to write alt text that screen readers love
Good alt text accessibility practice follows one simple rule: describe what the image communicates, not what it looks like.
- Be specific and concise — one to two sentences is usually enough
- Describe function for interactive images (buttons, links), not appearance
- Include the key data point for charts and infographics
- Skip phrases like “image of” or “photo of” — screen readers already announce the element type
- Do not repeat surrounding body text verbatim — screen reader users will hear the same content twice
The WebAIM Screen Reader User Survey consistently reports that missing or inadequate alt text is among the most frustrating barriers users encounter online.
Audit and fix alt text across your WordPress site
Most WordPress sites accumulate images without alt text over months or years — especially images uploaded before the owner understood why alt text accessibility mattered.
Alt text can be added in three places in WordPress:
- Media Library — select any image and update the Alt Text field in the right panel
- Block Editor — click an image block and use the Alt Text field in the sidebar
- Page builders — Bricks, Elementor, and others each provide a dedicated alt text input per image element
For e-commerce sites, WooCommerce product images carry additional accessibility weight — visually impaired users cannot evaluate a product they cannot understand, which is a direct revenue gap as well as a compliance issue.
For sites with hundreds of images, manual remediation is not practical. Image Alt Text Pro generates accurate, contextual alt text for every image in your media library using AI — including images uploaded before you set up any alt text workflow. You can process your entire library in one click from the bulk processing feature.
Start with the free audit: the Image Alt Text plugin on WordPress.org identifies every image on your site with missing or empty alt text at no cost.
Alt text accessibility – final verdict
- Alt text is the only mechanism by which screen readers communicate image content to visually impaired users
- Missing or generic alt text leaves screen reader users with meaningless filenames, silence, or “image, image”
- WCAG 1.1.1 requires text alternatives for all non-decorative images — it is a legal baseline, not a suggestion
- Linked images and image buttons are the highest-impact failure points to fix first
- Decorative images should use
alt=""to suppress unnecessary screen reader announcements