What is Alt for Image in Html and Accessibility

Alt text is a crucial aspect of HTML, and it's essential for accessibility. It provides a text description of an image, which is read aloud by screen readers for visually impaired users.

The alt attribute is used to specify the alternative text for an image. This attribute is a must-have for images that convey important information or have a functional role on the page. As mentioned in the article, an alt attribute is required for images that are used as links or buttons.

For example, if an image is used as a button, the alt text would describe its function, such as "Submit Form" or "Login Button". This helps screen readers to accurately convey the image's purpose to users who cannot see it.

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In HTML, ALT text is inserted into the ALT attribute within the IMG tag. This is a crucial step in making images accessible to screen readers.

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ALT text is a screen reader friendly text alternative description of an image. It can be implemented differently across document types.

There are several terms used to describe ALT text, including ALT text, ALT attribute, and ALT "Tag". These terms are often used interchangeably, but ALT attribute specifically refers to the ALT text inserted into the ALT attribute within the IMG tag.

Here's a breakdown of the key terms:

The purpose of ALT text is to add a text description to an image on a Web page. This description is crucial for screen reader users who rely on it to understand the content of an image.

ALT text is used for all images, graphical bullets, and graphical horizontal rules. It's a must-have for any image on your website.

The ALT text is displayed when an image is broken or when all images have been disabled in visual browsers like Firefox. This ensures that users don't miss out on important information.

Screen reader users access the ALT text to get a text equivalent of images. This is especially important for users who are visually impaired or have other disabilities.

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Implementing the alt attribute is a straightforward process, but it's essential to get it right. The alt attribute can be implemented depending on the context.

For example, HTML img alt attribute works only when the image link is broken or the image cannot be displayed. This is shown in the example where a broken image is displayed, and the output of the alt attribute is visible.

The text in the alt attribute is used to replace the image when it cannot be loaded, without changing the intended meaning of the page's contents. This is in line with the W3C's web content accessibility guidelines, which state that the alt attribute is used to convey the meaning and intent of the image.

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The alt attribute can be implemented in various ways, depending on the context.

You can use the alt attribute to provide a short and concise description of the image, which will be read out by screen readers and displayed by text-based web browsers.

The alt attribute is intended to convey the meaning and intent of the image, rather than being a literal description of the image itself.

For example, an alt attribute for an image of an institution's logo should convey that it is the institution's logo, rather than describing details of what the logo looks like.

A screen reader such as Orca will read out the alt text in place of the image, while a text-based web browser such as Lynx will display the alt text instead of the image.

The alt attribute improves search engine optimization and allows image-specific search engines, such as Google Images, to search for and display relevant images.

Here are some examples of how to implement the alt attribute:

Note: The W3C recommends using CSS to render decorative images, rather than HTML.

The alt attribute contains a single value, which is a text description of the image. This description should succinctly convey the content or function of the image.

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The key is to be concise, yet informative. For example, an alt attribute for an image of an institution's logo should convey that it is the institution's logo rather than describing details of what the logo looks like.

Here are some general guidelines to keep in mind:

For instance, if you have an image of text, it's best to have the exact same text in the alt attribute. This way, screen readers can accurately convey the information to users.

If images fail to load, ALT text will show what the images would have said in a browser such as Firefox. This is especially important for users who rely on screen readers to navigate the web.

Without the ALT text, no one can know what the content of the image would have been, and a screen reader will simply say “Image” five times.

WCAG 2.0 Guideline 1.1.1 states that all non-text content must have a text alternative that serves the equivalent purpose. This guideline is crucial for ensuring that all users can access and understand the content of a website.

Any text used in an image should follow legibility and contrast guidelines to ensure it's easily readable by users.

Image captions are an essential part of making images accessible to everyone, including those who cannot see them. They provide a brief description of the image.

A linked image is an image that is linked to another webpage. For example, an image of a product on an e-commerce website might be linked to the product's details page.

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Informative images are a crucial part of a page's context, and they need alt text to provide a fulfilling experience for people using assistive technology.

To write good alt text, consider the context of the image and what additional content it supports. The tone of the alt text should match the tone of the accompanying content.

A well-written alt text should be concise, ideally no longer than 100 characters, to avoid a poor user experience for those using screen readers. If the image requires a lengthier description, it's better to describe the image in the content and provide a shorter alt text.

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Contrary to popular belief, alt text doesn't need to be an objective description, it can convey nuances, details, and emotions if they are relevant to the user experience. For example, an image of King Henry VIII of England could be described as "King Henry VIII of England looking stern and wearing lavish royal clothing" in an article about the history of the Royal family of England.

If the image is used in a different context, like an article focusing on royal fashion in the XX century England, an appropriate alt text could be "King Henry VIII of England wearing a fur-trimmed hat and cape, bedazzled shirt and golden jewelry."

In general, the alt text should match the tone of the accompanying content, and it's okay to convey emotions and nuances if they are relevant to the user experience.

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Any information about the image, such as copyright information, image source or extra information should be placed in the caption text below the image, not in the ALT text.

The caption is where you can add additional context, like the image's title, artist, or date it was created, as seen in the example: "Painting “Washington and Lafayette at Valley Forge” by John Ward Dunsmore from 1907. Image courtesy of the Library of Congress."

The ALT text, on the other hand, is meant to provide a brief description of the image for screen readers and search engines, so they can understand what the image is about.

Using an image as a linked logo is a common practice, especially when you want to lead users to a specific webpage. The image used in Example 1 shows how this can be done.

The image in Example 1 contains a link that leads to Siteimprove's webpage. This link is shown without any other link text, making it a simple yet effective way to direct users.

The alternative text "Siteimprove home" is used to indicate where the link will take the user. This is an important detail, as it helps users understand what to expect when they click on the image.

This approach can be a great way to create a visually appealing logo that also serves as a link.

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