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Image, area and button with image tags should have an "alt" attribute

Web:ImgWithoutAltCheck

The alt attribute provides a textual alternative to an image.

It is used whenever the actual image cannot be rendered.

Common reasons for that include:

It is also very important to not set an alt attribute to a non-informative value. For example <img ... alt="logo"> is useless as it doesn’t give any information to the user. In this case, as for any other decorative image, it is better to use a CSS background image instead of an <img> tag. If using CSS background-image is not possible, an empty alt="" is tolerated. See Exceptions bellow.

This rule raises an issue when

Noncompliant Code Example

<img src="foo.png" /> <!-- Noncompliant -->
<input type="image" src="bar.png" /> <!-- Noncompliant -->
<input type="image" src="bar.png" alt="" /> <!-- Noncompliant -->

<img src="house.gif" usemap="#map1"
    alt="rooms of the house." />
<map id="map1" name="map1">
  <area shape="rect" coords="0,0,42,42"
    href="bedroom.html"/> <!-- Noncompliant -->
  <area shape="rect" coords="0,0,21,21"
    href="lounge.html" alt=""/> <!-- Noncompliant -->
</map>

Compliant Solution

<img src="foo.png" alt="Some textual description of foo.png" />
<input type="image" src="bar.png" alt="Textual description of bar.png" />

<img src="house.gif" usemap="#map1"
    alt="rooms of the house." />
<map id="map1" name="map1">
  <area shape="rect" coords="0,0,42,42"
    href="bedroom.html" alt="Bedroom" />
  <area shape="rect" coords="0,0,21,21"
    href="lounge.html" alt="Lounge"/>
</map>

Exceptions

<img> tags with empty string alt="" attributes won’t raise any issue. However this technic should be used in two cases only:

When the image is decorative and it is not possible to use a CSS background image. For example, when the decorative <img> is generated via javascript with a source image coming from a database, it is better to use an <img alt=""> tag rather than generate CSS code.

<li *ngFor="let image of images">
    <img [src]="image" alt="">
</li>

When the image is not decorative but it’s alt text would repeat a nearby text. For example, images contained in links should not duplicate the link’s text in their alt attribute, as it would make the screen reader repeat the text twice.

<a href="flowers.html">
    <img src="tulip.gif" alt="" />
    A blooming tulip
</a>

In all other cases you should use CSS background images.

See W3C WAI Web Accessibility Tutorials for more information.

See