HTML Image Elements: Essential Attributes and Best Practices

The HTML <img> element is fundamental to web development, allowing developers to embed images into web pages. Based on the training content, there are four essential attributes that should be included with every image element to ensure proper functionality, accessibility, and performance.

The Four Essential Image Attributes

1. Source (src) Attribute

The src attribute tells the browser which image file to load.

Example of HTML IMG tag with source, alt text, width, and height attributes for responsive design

This can be either:

• An absolute URL pointing to an external resource

• A relative path to a local image file

html

<img src="https://example.com/images/dog.jpg">

2. Alt Attribute for Accessibility

The alt attribute provides alternative text that serves as a substitute when the image cannot be displayed. This is crucial for:

• Screen reader users who are blind or visually impaired

• Situations where images fail to load

• Search engine optimization

Best practices for alt text:

• Be descriptive and concise - focus on what's important about the image

• Avoid redundant phrases like "photo of" or "image of"

• Can be creative, funny, or poetic when appropriate

• Leave blank (alt="") for purely decorative images to avoid redundancy

Illustration demonstrating alt text usage for an image of a crowd of people walking with example HTML code

html

<img src="dog.jpg" alt="Shiny black dog looking pensive">

3. Width and Height Attributes

The width and height attributes specify the image dimensions in pixels. These values should match the actual pixel dimensions of the image file.

html

<img src="dog.jpg" alt="Shiny black dog looking pensive" width="400" height="300">

Important notes:

• Values are specified as numbers only (no units required)

• The order of attributes doesn't matter in HTML

• These dimensions should reflect the actual image file size

Why Width and Height Matter

While images will display correctly without width and height attributes, including them provides significant performance benefits:

Layout Stability

When browsers don't know image dimensions in advance, they must:

1. Download the image file first

2. Read the file to determine dimensions

3. Recalculate and adjust the page layout

4. Potentially shift content around existing text

This creates the frustrating experience of content jumping while reading, as images load and push text around the page.

Performance Optimization

By specifying dimensions upfront, browsers can:

• Reserve the correct amount of space immediately

• Calculate layout before images finish downloading

• Prevent content shifting and layout thrashing

• Provide a smoother user experience

Complete Image Element Example

Here's a properly structured image element with all four essential attributes:

html

<img src="https://example.com/dog.jpg" alt="Shiny black dog looking pensive" width="400" height="300">

When to Use Empty Alt Text

There are specific scenarios where empty alt text is appropriate:

Example: Company Logo with Text

html

<h1>Happy Dog Daycare</h1> <img src="logo.png" alt="" width="100" height="50">

In this case, since the company name is already present in the heading, having the screen reader announce both "Happy Dog Daycare" and "happy dog" would be redundant and diminish the user experience.

Important: Always include the alt attribute, even if empty. Omitting it entirely may cause screen readers to announce the image filename instead.

The four essential attributes - src, alt, width, and height - work together to create accessible, performant, and user-friendly web experiences. Proper implementation prevents layout shifting, supports assistive technologies, and ensures images contribute positively to the overall web experience.