Alt tags (alternative text) are concise descriptions embedded in the HTML code of an image, crucial for web accessibility, SEO, and user experience. To write effective alt tags, focus on accurately describing the image's content and purpose in a brief, specific manner, keeping it to one or two sentences without using redundant phrases like "image of."
What Are Alt Tags and Why Are They Important?
Alt tags, formally known as alt attributes, are short textual descriptions that provide context for images on a webpage. They serve multiple vital functions:
- Accessibility: Screen readers use alt text to describe images to visually impaired users, allowing them to understand the content and purpose of an image that they cannot see.
- Search Engine Optimization (SEO): Search engines cannot "see" images, so they rely on alt text to understand what an image depicts. This helps images rank in image search results and contributes to the overall SEO of your webpage.
- User Experience (UX): If an image fails to load due to a slow internet connection or a broken link, the alt text is displayed in its place, providing users with information about what was supposed to be there.
Core Principles for Crafting Effective Alt Tags
Writing good alt tags isn't just about describing an image; it's about conveying its meaning and purpose within the context of your content.
Be Descriptive and Specific
Your alt tag should accurately describe what's in the image. Think about the key visual elements and how they relate to the surrounding content.
- Describe the subject, action, and any relevant text within the image.
- Focus on details that are critical to understanding the image's message.
Keep It Concise and Relevant
Aim for brevity while being informative. Your alt tag should be brief, typically no more than one or two concise sentences. Focus on conveying the core message or the most important elements that make the image relevant to the content, rather than detailing every minor visual aspect. Think about why you included the image and what essential information it provides.
Integrate Keywords Naturally
Where appropriate, include relevant keywords that help search engines understand the image's context and relevance to your page. However, avoid "keyword stuffing," which can harm your SEO and user experience.
- Use keywords only if they genuinely fit the image description.
- Ensure the alt text still reads naturally and provides value to a user.
Avoid Redundancy
There's no need to preface your description with phrases like "image of" or "picture of." Screen readers automatically identify it as an image, making these words redundant and taking up valuable character space.
Provide Context
The best alt tags connect the image to the surrounding text. Consider what information the image adds to the page and describe it from that perspective.
Practical Examples of Good and Bad Alt Tags
Here's a comparison to illustrate the difference between effective and ineffective alt tags:
| Image Description | Poor Alt Tag | Good Alt Tag | Why It's Good |
|---|---|---|---|
| A golden retriever running through a grassy park. | dog |
Golden retriever happily running through a sunny park |
Specifics breed, action, emotion, and setting. |
| A bar chart showing website traffic increased by 20% in Q3. | chart |
Bar chart showing a 20% increase in website traffic during Q3 |
Describes the type of chart and the key data point it represents. |
| A company logo for "InnovateTech." | logo |
InnovateTech company logo |
Identifies it as a logo and states the company name. |
| A 'Submit' button on a form. | button |
Submit order |
Describes the action the button performs, not just that it's a button. |
| A decorative swirl pattern. | blue swirl design |
alt="" |
As a purely decorative element, an empty alt tag is appropriate to avoid screen reader clutter. |
Special Cases for Alt Tags
Some image types require a slightly different approach:
Decorative Images
For images that are purely decorative and add no significant information to the content (e.g., background patterns, dividers, or spacing images), use an empty alt attribute: alt="". This tells screen readers to skip the image, preventing unnecessary clutter for users.
Images as Links
If an image acts as a link, the alt text should describe the destination or function of the link, not just the image itself. For example, for an image linking to a product page, the alt text could be alt="View product details for [Product Name]".
Complex Images (Graphs, Infographics)
For detailed charts, graphs, or infographics, the alt tag should provide a brief summary of the image's main point. A more comprehensive description of the data or information should be provided in the surrounding text or via a link to a separate, detailed description.
How to Implement Alt Tags
Alt tags are added within the <img> HTML element.
<img src="your-image.jpg" alt="Your descriptive alt text here">Most Content Management Systems (CMS) like WordPress, Shopify, or Squarespace provide a dedicated field to add alt text when you upload or embed an image, simplifying the process.
Common Mistakes to Avoid
- Missing Alt Tags: Leaving alt tags empty for non-decorative images hurts accessibility and SEO.
- Keyword Stuffing: Overloading alt tags with keywords is detrimental and provides a poor user experience.
- Too Generic: "Image," "picture," or simply repeating the file name offers no value.
- Too Long: While there's no strict character limit, excessively long alt tags can be cumbersome for screen reader users. Aim for conciseness.
- Irrelevant Descriptions: Ensure the alt text accurately reflects the image and its context.
Tools and Resources
- WebAIM: Offers comprehensive guidelines on web accessibility, including alt text best practices: WebAIM Alt Text
- Google Search Central: Provides insights into how Google handles images for search: Google Images best practices
- W3C: The World Wide Web Consortium's specifications for HTML and accessibility: W3C Alt Decision Tree
By following these guidelines, you can create effective alt tags that enhance the accessibility, SEO, and overall user experience of your website.
