How to Add Alt Tags to Images: A Complete Guide for Better SEO and Accessibility

Learn how to add alt tags to images to boost your website’s SEO and accessibility. Alt tags, also known as alt text or alt attributes, are essential for describing images to search engines and screen readers. This 2,500-word guide covers everything web developers, content creators, and SEO professionals need to know about image alt text, including step-by-step instructions, code examples, and best practices.

What Are Alt Tags and Why Do They Matter?

Alt tags are HTML attributes added to image tags to describe their content. The term "alt tag" is commonly used, but technically, it’s an alt attribute within an <img> tag. For example:

<img src="dog.jpg" alt="A golden retriever playing fetch in a park">

Alt text serves multiple purposes:

SEO: Helps search engines understand image content, improving rankings for image SEO.
Accessibility: Provides descriptions for visually impaired users via screen readers.
Fallback: Displays text if an image fails to load.

Alt tags differ from captions (visible text below images) and title attributes (tooltip text on hover). They’re critical for web accessibility standards like WCAG 2.1/2.2 and legal compliance (e.g., ADA).

Placement suggestion: Include a screenshot of an image with alt text displayed in a screen reader interface.

SEO Benefits of Proper Alt Tag Implementation

Proper alt tags enhance SEO alt tags by:

Improving image search visibility on Google Images.
Providing context for search engine crawlers, boosting page relevance.
Supporting keyword strategies with alt tags for SEO optimization.

For example, an e-commerce site selling running shoes can use alt text like “Men’s blue Nike running shoes on a trail” to rank for related queries. Avoid keyword stuffing, as it harms user experience and may trigger penalties.

Accessibility Impact: Making Your Site Inclusive

Alt tags are vital for screen reader accessibility. Visually impaired users rely on tools like NVDA or VoiceOver to read alt text aloud. Without alt tags, images are invisible to these users, violating accessibility alt text principles.

Legal frameworks like the ADA and WCAG 2.1/2.2 mandate accessible websites. Non-compliance risks lawsuits, especially for businesses. Proper alt tags ensure inclusivity and demonstrate commitment to web accessibility standards.

How to Write Effective Alt Tags

Writing how to write good alt tags involves balancing descriptiveness and brevity. Follow these guidelines:

Be Descriptive: Describe the image’s content and function (e.g., “A bar chart showing 2025 sales data”).
Keep It Concise: Aim for 125 characters or less to accommodate most screen readers.
Avoid Redundancy: Don’t start with “Image of” or “Picture of.”
Context Matters: Tailor alt text to the page’s purpose (e.g., product images vs. decorative icons).
Empty Alt Tags: Use alt="" for decorative images to signal screen readers to skip them.

Example: For a blog header image, use alt="A laptop on a desk with coding software open" instead of alt="Image of a laptop."

Step-by-Step Guide: Adding Alt Tags in Different Platforms

Alt Tags in HTML: Manual Implementation

To add alt attribute HTML, include the alt attribute in the <img> tag:

<img src="logo.png" alt="Cheeeck.com logo with blue checkmark">

Steps:

Identify the image’s purpose (informative or decorative).
Write concise, descriptive alt text.
Add the alt attribute to the <img> tag.
Test with a screen reader or validator.

Placement suggestion: Include a screenshot of HTML code in a text editor.

Adding Alt Tags in WordPress

For WordPress alt tags, follow these steps:

Upload an image in the WordPress Media Library.
Click the image to edit details.
Enter alt text in the “Alt Text” field.
Save changes and insert the image into your post or page.

To bulk-edit alt tags:

Go to Media > Library.
Select images and use the “Edit” option to add alt text.

For developers, automate alt text with a functions.php modification:

function auto_alt_text($metadata, $attachment_id) {
    if (!get_post_meta($attachment_id, '_wp_attachment_image_alt', true)) {
        $filename = get_the_title($attachment_id);
        update_post_meta($attachment_id, '_wp_attachment_image_alt', sanitize_text_field($filename));
    }
    return $metadata;
}
add_filter('wp_generate_attachment_metadata', 'auto_alt_text', 10, 2);

This sets the image title as alt text if none is provided.

Placement suggestion: Include a screenshot of the WordPress Media Library alt text field.

Alt Tags in Other CMS Platforms

Shopify:
1. Go to Products > Edit Product.
2. Click an image and add alt text in the “Alt Text” field.
3. Save changes.
Squarespace:
1. Edit a page and select an image.
2. Add alt text in the “Image Description” field.
3. Apply and save.
Wix:
1. Click an image in the editor.
2. Go to Settings > Alt Text.
3. Enter alt text and save.

Each CMS prioritizes image optimization differently, so check documentation for specifics.

Common Alt Tag Mistakes to Avoid

Avoid these pitfalls for alt tag best practices:

Keyword Stuffing: E.g., alt="SEO alt tags image optimization best alt text" is spammy.
Generic Text: E.g., alt="photo" lacks context.
Missing Alt Tags: Leaving alt attributes blank for informative images harms accessibility.
Overly Long Text: Exceeding 125 characters may truncate in screen readers.
Ignoring Decorative Images: Use alt="" instead of omitting the attribute.

Placement suggestion: Include a table comparing correct vs. incorrect alt tag examples.

Alt Tag Best Practices and Guidelines

Follow these alt text guidelines:

Informative Images: Describe content and function (e.g., “A pie chart showing budget allocation”).
Decorative Images: Use alt="" to skip screen reader narration.
Complex Images: For charts or infographics, provide a text summary in the alt tag and a detailed description nearby.
E-commerce: Include product details (e.g., “Blue ceramic mug with floral design”).
Social Media: Add alt text for platform accessibility (e.g., Twitter’s image description feature).

For alt tags for SEO optimization, incorporate relevant keywords naturally, like “WordPress alt tags tutorial” for a tutorial image.

Tools for Testing and Optimizing Alt Tags

Use these tools to ensure image alt text quality:

WAVE: Browser extension for accessibility audits.
axe DevTools: Checks alt tags against WCAG standards.
Google Lighthouse: Evaluates SEO and accessibility.
Screen Readers: Test with NVDA (Windows) or VoiceOver (Mac).
Alt Text Tester: Chrome extension to view alt text on hover.

Call-to-Action: Audit your website’s alt tags using WAVE or Lighthouse. Visit Cheeeck.com for more SEO alt tags resources.

Advanced Tips for Alt Tags

Complex Images: For graphs, use alt text like “Line graph showing website traffic from January to June 2025” and link to a data table.
E-commerce Optimization: Include brand, color, and product type (e.g., “Samsung Galaxy S25 in black”).
Dynamic Alt Tags: Use JavaScript to generate alt text for dynamic content:

document.querySelectorAll('img').forEach(img => {
    if (!img.alt) {
        img.alt = img.src.split('/').pop().split('.')[0].replace(/-/g, ' ');
    }
});

CSS Styling: Style alt text display for fallback scenarios:

img[alt] {
    font-size: 14px;
    color: #333;
    display: block;
}

Social Media: Platforms like Instagram and LinkedIn support alt text for accessibility alt text.

Call-to-Action

Ready to improve your site’s image SEO and accessibility? Start by auditing your website with Cheeeck.