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What is Alt Tag? Why They Are Important?

Apr 12 2024 by Oskay Günaçar

An Alt tag, short for "alternative text," is a crucial element in web design and accessibility. It serves as a textual descriptor of an image on a webpage. When an image is not displayed or when a user employs screen reading tools due to visual impairment, the Alt tag provides a description of the image. This text plays a vital role in ensuring web content is accessible to all users, including those with disabilities.

Syntax of Alt Tags

An Alt tag is embedded within the HTML code of a webpage. It's typically found within the <img> tag, an HTML element used to embed images. The Alt attribute is added to this tag, and the value assigned to it is the descriptive text. For instance, <img src="example.jpg" alt="A descriptive text of the image">. This structure ensures that if the image fails to load, or if a user can't visually perceive the image, the descriptive text is displayed or read out loud by screen reading software.

Here's a breakdown of the syntax:

  1. Basic Structure: The basic structure of an Alt tag within an image tag looks like this:

    <img src="url_of_the_image.jpg" alt="Descriptive text of the image">

    In this structure:

    • <img> is the tag used to insert an image.
    • src (source) attribute specifies the path or URL to the image file.
    • alt is the attribute used for the alternative text.
  2. Alt Attribute: The alt attribute is where the alternative text is placed. This text should be a concise and accurate description of the image.

    For example:

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

  3. Handling Decorative Images: If an image is purely decorative and adds no informational content to the site, you can use an empty alt attribute. This is done by still including the alt attribute but without any text, like so:

    <img src="decorative_border.jpg" alt="">

    This approach is used to tell assistive technologies like screen readers to ignore the image.

Why Is the ALT Attribute Needed For?


The ALT attribute as an essential component in web design, serving two primary purposes: enhancing web accessibility and aiding in search engine optimization (SEO).

Enhancing Web Accessibility

The primary role of the ALT attribute is to improve web accessibility. It provides a text alternative for images on web pages, which is crucial for users with visual impairments. When images cannot be seen or loaded, the ALT text describes the image, ensuring that all users, regardless of their ability to see the image, can understand its content and context. This is particularly important for users who rely on screen readers – assistive technology that reads aloud the content of a web page. The ALT text is read by these screen readers, allowing visually impaired users to comprehend what the image is about.

For example, consider an image of a chart on a webpage. If a visually impaired user is accessing the site with a screen reader and the chart lacks an ALT attribute, the user would miss out on the information conveyed by the chart. However, with an appropriate ALT text, the user can understand the chart's content as the screen reader verbalizes the ALT text.

Aiding in Search Engine Optimization (SEO)

The ALT attribute also plays a significant role in SEO. Search engines, which can't "see" images in the way humans do, rely on ALT text to understand and index an image's content. ALT text helps search engines contextualize images and understand how they relate to the surrounding content on a webpage. This is crucial for image search results; images with well-written ALT text are more likely to appear in relevant searches.

Additionally, the ALT attribute can improve the overall user experience when images fail to load on a webpage. In such cases, the ALT text is displayed in place of the image, providing context and maintaining the flow of information on the page.

ALT Tag vs. Title Tag In Images: What Is The Difference?

The ALT tag and the Title tag in images serve different purposes and are used in different contexts within HTML. Understanding the distinction between these two is important for effective web development and design.

ALT Tag (Alternative Text)

  • Purpose: The ALT tag is primarily used for accessibility. It provides a text alternative for images for users who are unable to see them. This includes users with visual impairments who use screen readers, as well as situations where the image fails to load on a webpage.
  • Syntax: The ALT tag is an attribute within the <img> element in HTML. For example: <img src="image.jpg" alt="Description of the image">.
  • SEO Impact: The ALT tag is important for search engine optimization. Search engines use the ALT text to understand the content of an image and how it relates to the surrounding text on a webpage. Well-crafted ALT text can improve a website's search engine ranking, particularly in image search results.
  • Accessibility Compliance: Including ALT text is a requirement for compliance with web accessibility standards like the Web Content Accessibility Guidelines (WCAG).

Title Tag (Title Attribute)

  • Purpose: The Title tag in images is used to provide additional information about an image, typically displayed as a tooltip when the user hovers over the image with a mouse. This can enhance user experience by offering extra context or information.
  • Syntax: The Title tag is also an attribute within the <img> element, but it serves a different purpose than the ALT tag. For example: <img src="image.jpg" title="Additional information about the image">.
  • SEO Impact: The Title tag has a much lesser impact on SEO compared to the ALT tag. While it can provide context, search engines primarily rely on ALT text to understand image content.
  • Accessibility: The Title tag is less critical for accessibility than the ALT tag. Screen readers may or may not read out the Title attribute, and it is not a substitute for ALT text.

In summary, while both the ALT and Title tags are used within image tags in HTML, their purposes are distinct. The ALT tag is essential for accessibility and SEO, providing a text alternative for images. The Title tag, on the other hand, is used to offer additional information or context and is displayed as a tooltip on most browsers. For optimal web accessibility and SEO, it's important to use the ALT tag correctly and thoughtfully, while the Title tag can be used as an optional supplement for enhancing user experience.

Importance of Alt Tags For Web Accessibility

The importance of Alt tags for web accessibility cannot be overstated. These tags play a crucial role in ensuring that digital content is inclusive and accessible to all users, particularly those with visual impairments. Below are the key reasons why Alt tags are vital for web accessibility:

  1. Enabling Screen Reader Accessibility: Alt tags provide descriptions of images for users who rely on screen readers. These assistive technologies read out loud the contents of a webpage, including the Alt text associated with images. Without Alt tags, visually impaired users may miss critical information conveyed through images, leading to an incomplete understanding of the webpage content.

  2. Fulfilling Legal and Ethical Standards: Many countries have laws and regulations, such as the Americans with Disabilities Act (ADA) in the United States, that require digital content to be accessible to people with disabilities. Alt tags are part of these requirements. By including Alt tags, website owners not only comply with these legal standards but also uphold ethical standards of inclusivity and equal access.

  3. Facilitating Better User Experience in Varied Situations: Besides benefiting users with visual impairments, Alt tags also enhance the user experience in situations where images fail to load due to slow internet connections or technical glitches. Instead of seeing a blank space or a broken image icon, users see a descriptive text, which keeps the flow of information uninterrupted.

  4. Providing Contextual Information: In some cases, images may contain critical information or contribute significantly to the content's context. Alt tags ensure that this information is not lost to users who cannot see the images, thereby maintaining the content's integrity and intended message.

  5. Supporting Diverse User Needs: Beyond those with visual impairments, Alt tags assist users with cognitive disabilities who may use text-to-speech software, users in noisy environments where images might not be easily viewed, and those who prefer textual over visual information for various reasons.

  6. Enhancing Navigation: For users navigating a website with a keyboard or through voice commands, Alt tags can provide necessary cues about where the links within the images will lead, improving the overall navigability of the website.

In conclusion, Alt tags are a fundamental element in making web content accessible to a diverse range of users. They ensure that the web remains an inclusive space, where information is available to everyone, regardless of their physical abilities or the limitations of their environment. By implementing Alt tags effectively, web developers and content creators can significantly enhance the accessibility and usability of their websites.

Importance of Alt Tags For SEO

The importance of Alt tags for Search Engine Optimization (SEO) is significant, as they play a crucial role in how search engines understand and rank web content. Here are the key ways in which Alt tags contribute to SEO:

  1. Improving Image Indexing: Search engines, like Google, use web crawlers that read and index web pages. These crawlers cannot "see" images in the way humans do, so they rely on Alt tags to interpret what an image is about. By providing a clear and concise description in the Alt tag, you help search engines index your images more effectively, making them more likely to appear in image search results.

  2. Enhancing Context and Relevance: Alt tags help search engines understand the context in which an image is used. This understanding is crucial for ranking the relevancy of a webpage in search results. An image with an Alt tag that closely aligns with the surrounding content contributes positively to the overall relevance of the page.

  3. Boosting Keyword Optimization: Alt tags offer an opportunity to include relevant keywords in your webpage. When you use keywords appropriately in Alt tags, you improve your page's chances of ranking higher for those terms. However, it's essential to avoid keyword stuffing (overusing keywords), as this can lead to penalties from search engines.

  4. Improving User Experience: User experience is a significant factor in SEO. Websites that are user-friendly tend to rank higher in search results. When images fail to load on a webpage, the Alt text ensures that users still understand what image was supposed to be there, contributing to a better overall user experience.

  5. Aiding in Accessibility and Compliance: Search engines increasingly consider the accessibility of web content when ranking pages. Websites that are accessible to users with disabilities, including those who use screen readers, may receive favorable ranking. Since Alt tags are a critical component of web accessibility, their proper use can positively influence SEO.

  6. Enhancing Mobile Experience: With the increasing use of mobile devices for internet access, the role of Alt tags has expanded. Slow mobile data speeds or limited bandwidth might cause images to load incompletely or not at all. Alt tags ensure that the content and purpose of these images are still conveyed, improving the mobile browsing experience, which is a factor in SEO.

In summary, Alt tags are a vital tool in the SEO toolkit. They help search engines understand and appropriately rank web content, contribute to a better user experience, and ensure content accessibility. Proper use of Alt tags can significantly improve a website's visibility and ranking in search engine results.

What Content Should the ALT Tags Have?

Crafting effective ALT text involves several key considerations to ensure it is both informative and functional.

Descriptive and Contextual Relevance

The ALT text should accurately describe what is shown in the image. This description should be concise yet detailed enough to convey the image's content and purpose within the context of the surrounding text. For instance, if the image is a chart illustrating sales trends, the ALT text should describe the type of chart and the trend it shows, such as "Bar chart showing an increase in sales for the first quarter."

Incorporate Keywords Strategically

Including relevant keywords in the ALT text can aid in SEO, as it helps search engines understand the image. However, the primary purpose of ALT text is to describe the image, so keyword inclusion should feel natural and relevant to the image's content. Avoid keyword stuffing, as this can negatively impact SEO and user experience.

Handling Decorative Images

For images that are purely decorative and do not add informational content to the page, such as borders or stylistic elements, the ALT text can be left empty. This approach tells screen readers to skip these images, preventing unnecessary clutter in the auditory experience of visually impaired users.

Length of ALT Text

The ALT text should be brief and to the point. A general guideline is to keep it under 125 characters. This length is sufficient to convey necessary information without being overly verbose, making it more usable for screen reader users and search engines.

Avoid Redundant Phrases

Phrases like "image of" or "graphic of" in the ALT text are generally unnecessary, as screen readers already announce the presence of an image. Directly starting with the description is more efficient and user-friendly.

Describe Functional Images Appropriately

If an image is used as a button or link, the ALT text should describe the function, not just the appearance. For example, for an image used as a search button, ALT text like "Search" is more appropriate than "Magnifying glass."

In summary, the ALT tag content should provide an accurate, concise description of the image, contextualized within the webpage content. It should be thoughtfully crafted to enhance user experience for those using screen readers, while also being mindful of SEO best practices. Effective ALT text contributes significantly to making web content accessible, inclusive, and optimized for search engine rankings.

Oskay Günaçar
Oskay Günaçar is a Technical SEO expert and backend developer. His main areas of interest are back-end programming, Python, Django, Go, semantic SEO, technical SEO. With more than 5 years of SEO experience, he has held SEO specialist positions at İkiler, Webtures, Boosmart, and companies, and has been involved in numerous projects as an outsourced expert. Through the TechSEOHub website, he aims to share the expertise and experience he has gained from managing and developing (SEO) processes for many successful and large websites in the industry, and to produce content for easy access to accurate and high-quality information.