Cookies on the Evinced Knowledge Base

We'd like to set Google Analytics cookies to learn how people use the Knowledge Base, so we can improve it. We set them only if you accept.

Skip to main content
Digital Accessibility Knowledge Base

alt-text-is-too-long

Web validation

alt text should not be longer than 140 characters.

Alt text helps assistive technology users understand the purpose of an image. When alt text is very long, it can be hard to follow in one read-through and tedious on repeated navigation. Some assistive technologies may not reliably announce very long alt text. Alt text also tends to become overly detailed when it gets long, which can distract from the image's main purpose in context. There is no official character limit for alt text. This validation uses 140 characters as a practical guideline.

Pass Patterns

Short, purpose-focused alt text

The alt value is short and focuses on the image's purpose in context.

HTML
<img src="/images/shipping.png" alt="Standard shipping delivery truck icon" />

Concise alt with a separate long description

The alt is concise, and a longer description is provided separately with aria-describedby.

HTML
<img
    src="/images/shipping.png"
    alt="Shipping options chart"
    aria-describedby="shipping-details"
/>


<div id="shipping-details">
    Standard: 5 to 7 business days. Express: 2 to 3 business days. Overnight: next day.
</div>

Fail Patterns

Alt text overloaded with detail

The alt is overly long and includes details that are not needed to understand the image's purpose.

HTML
<img
    src="/images/team.jpg"
    alt="A large group of people standing in a modern office space with tall windows, wearing company shirts, smiling, holding signs with the company name and several slogans, with balloons and decorations in the background to celebrate the launch..."
/>

Alt used as a long-form description

The alt is being used as a long description instead of a short alternative.

HTML
<img
    src="/images/product.png"
    alt="This is a screenshot of the product settings page. At the top left there is a navigation menu with items including Home, Projects, Billing, Security, and Integrations. In the main panel there are multiple sections with headings, toggles, and help text..."
/>

Try It Yourself

Using a screen reader

New to screen reader testing, or need a refresher?
Review this article first: Practical guides for using screen readers

  1. Load the page and open a screen reader.
  2. Navigate to the image.
  3. Listen to the announced alt text.

Expected results: The screen reader announces concise alt text that is easy to understand in one pass.

Actual results: The screen reader announces long alt text that is hard to follow and slows navigation.

Inspecting the browser dev-tools

  1. Open the page and inspect the image element.
  2. Open the Accessibility panel in your browser's dev tools.
  3. Review the computed accessible name, which usually comes from alt.

Expected results: The image's accessible name is short and focused.

Actual results: The image's accessible name is overly long because it comes from an excessive alt value.

FAQ

Why is this rule considered a best practice?

No WCAG success criterion sets a maximum alt length; SC 1.1.1 only requires a text alternative. Even so, short, focused alt text is easier to understand and faster to navigate. When a long description is truly needed, keep alt concise and provide the detail elsewhere, such as with aria-describedby and a describing element.

Why is this issue marked as Moderate?

Overly long alt text rarely blocks access, but it slows down screen reader and braille users, adds repetition fatigue, and risks inconsistent announcement across assistive technologies. Because images often repeat across pages, the friction adds up, so it is rated moderate.

Standards and Regulations

This issue is classified as "Best Practice," meaning it isn't tied to a specific WCAG success criterion or any other regulation or standard; however it still affects the experience of some users. These issues fall outside formal compliance requirements, yet addressing them improves usability and accessibility in practice.

Personas impacted by this issue

Learn More

Contents

Evinced is an enterprise digital accessibility testing platform that finds and tracks WCAG and ADA compliance issues in websites and mobile apps.