HTML Tag: A Complete Guide to Displaying Images on Web Pages

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HTML <img> Tag: A Complete Guide to Displaying Images on Web Pages

The HTML <img> tag is one of the most fundamental elements for creating visually appealing web pages. This self-closing tag allows you to embed images directly into your HTML documents, enhancing user experience and providing visual context to your content.

Basic Syntax and Structure

The <img> tag uses a simple, straightforward syntax:

html

<img src="image-source.jpg" alt="Image description" width="400" height="300">

Unlike most HTML elements, the <img> tag is self-closing, meaning it doesn't require a closing tag. Instead, all attributes are contained within the single opening tag, which ends with a forward slash in XHTML format.

Essential Attributes

The src Attribute

The src (source) attribute is the most critical component of the <img> tag. It specifies the path or URL to the image file you want to display. There are two ways to specify the image source:

Absolute URL: Links to an external image hosted on another website

html

<img src="https://www.example.com/images/photo.jpg" alt="External image">

Relative URL: Links to an image hosted within your own website

html

<img src="images/photo.jpg" alt="Local image"> <img src="/assets/images/photo.jpg" alt="Root-relative path">

The browser uses the src attribute to locate and request the image file from the server. If the path is incorrect or the image doesn't exist, browsers will display a broken image icon.

The alt Attribute

The alt (alternative text) attribute is equally important and required for proper HTML validation. This attribute serves multiple crucial purposes:

  • Accessibility: Screen readers use alt text to describe images to visually impaired users

  • SEO Benefits: Search engines use alt text to understand and index images

  • Fallback Content: If an image fails to load, the alt text is displayed instead

xml

<img src="company-logo.png" alt="TechCorp Company Logo">

Example HTML <img> tag usage showing src, alt, width, and height attributes to display an image on a webpage

Width and Height Attributes

The width and height attributes control the display dimensions of your image:

xml

<img src="sunset.jpg" alt="Beautiful sunset" width="800" height="400">

Key benefits of specifying dimensions:

  • Prevents layout shifts: Browsers can reserve space before the image loads

  • Improves page performance: Reduces reflow and repaint operations

  • Better user experience: Pages appear more stable during loading

You can specify dimensions in several ways:

  • HTML attributes: width="300" height="200"

  • CSS properties: style="width:300px;height:200px;"

  • CSS classes with defined dimensions

How the <img> Tag Works in Practice

Browser Rendering Process

When a browser encounters an <img> tag, it follows a specific 5-stage pipeline:

  1. Request/Fetch Stage: The browser immediately sends an HTTP request to retrieve the image from the specified src URL

  2. Download Stage: The image file is downloaded and stored in the browser's cache

  3. Decoding Stage: The compressed image file is converted into pixel data that can be displayed

  4. Rendering Stage: The image is positioned and styled according to CSS rules, then rendered on screen

  5. Repainting Stage: The page layout may be adjusted to accommodate the newly rendered image

HTML example showing the <img> tag with src, alt, title, width, and height attributes for displaying images

Loading Behavior

Modern browsers support advanced loading techniques through additional attributes:

Lazy Loading:

xml

<img src="below-fold.jpg" alt="Image below the fold" loading="lazy">

  • Defers image loading until the image approaches the viewport

  • Improves initial page load performance

  • Supported in Chrome 76+, Edge, Opera, and Firefox

Fetch Priority:

xml

<img src="hero-image.jpg" alt="Hero image" fetchpriority="high">

  • Controls the priority of image downloads relative to other resources

  • Values: high, low, or auto (default)

Responsive Images

For modern web development, you can create responsive images using additional attributes:

xml

<img src="logo.png" alt="Company logo" srcset="logo-retina.png 2x, logo-retina-lg.png 3x" width="200" height="150">

The srcset attribute allows browsers to select the most appropriate image based on device pixel density.

Common Image Formats

HTML supports various image formats, each optimized for different use cases:

  • JPEG: Best for photographs and complex images with gradients

  • PNG: Ideal for images with transparency, logos, and sharp edges

  • GIF: Perfect for simple animations and images with limited colors

  • SVG: Scalable vector graphics for icons and simple illustrations

  • WebP: Modern format offering superior compression

Best Practices

Performance Optimization

  1. Always specify dimensions to prevent layout shifts

  2. Optimize file sizes through compression without sacrificing quality

  3. Use appropriate formats for different image types

  4. Implement lazy loading for images below the fold

Accessibility and SEO

  1. Write meaningful alt text that describes the image content and purpose

  2. Keep alt text concise but descriptive (typically under 100 characters)

  3. Use empty alt attributes (alt="") for decorative images

  4. Ensure proper contrast between images and surrounding text

Error Handling

When images fail to load, browsers display a broken image icon and the alt text. To minimize this:

  • Verify image paths are correct and accessible

  • Test images across different devices and network conditions

  • Provide meaningful alt text as a fallback

  • Consider using placeholder images during development

Example of using the HTML <img> tag with src and alt attributes to display an image on a webpage

Advanced Features

Image Maps

You can create clickable areas within images using image maps:

xml

<img src="world-map.jpg" alt="World Map" usemap="#worldmap"> <map name="worldmap"> <area shape="rect" coords="0,0,100,100" href="europe.html" alt="Europe"> </map>

Clickable Images

Transform images into links by wrapping them in anchor tags:

xml

<a href="gallery.html"> <img src="thumbnail.jpg" alt="View full gallery"> </a>

The HTML <img> tag is a powerful tool for web developers, offering both simplicity in basic usage and sophistication in advanced implementations. By understanding its core attributes and how browsers process images, you can create faster, more accessible, and visually appealing web pages that provide excellent user experiences across all devices and platforms.

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