Alt Text

The Purpose of Alt Text

Alt text is part of the HTML specification for images. It provides a textual alternative when the image cannot be seen. This is critical for accessibility. Screen readers read the alt text aloud to visually impaired users. It also appears when an image fails to load due to a broken link or slow connection.

Search engines use alt text as a signal to understand the image's content. This helps with image search and can provide context for the surrounding page. Alt text is not the same as a caption. Captions are visible to all users, while alt text is typically hidden unless needed.

How to Write Effective Alt Text

Writing good alt text is straightforward. Describe the image's content and function. Be specific but concise. For example, 'A black cat sitting on a red sofa' is better than 'Cat'. Avoid starting with 'image of' or 'picture of'. Screen readers already announce that it's an image.

If the image is decorative and adds no information, use an empty alt attribute (alt="") so screen readers skip it. For informative images, ensure the alt text conveys the same information as the image. Keep alt text under 125 characters when possible. Include relevant keywords only if they naturally fit. Do not stuff keywords.

For example, if you have a photo of a product, write 'Blue ceramic mug with a white handle on a wooden table' rather than 'Mug'. If the image contains text, include that text verbatim, such as 'Sign reading: Open 24 hours'. For complex images like charts, provide a brief summary and link to a longer description. For a bar chart showing sales by quarter, write 'Bar chart of quarterly sales: Q1 $10k, Q2 $15k, Q3 $12k, Q4 $18k' and link to a data table.

• Describe what you see.
• Mention any text in the image.
• Use proper punctuation.
• For links, describe the link destination.
• For complex images like charts, provide a brief summary and link to a longer description.

Alt Text and SEO: What You Need to Know

Alt text is a minor ranking factor for image search. Google uses it to understand the image's subject. However, it is not a major ranking signal for page content. The primary purpose is accessibility. Over-optimizing alt text with keywords can harm user experience and may be seen as spam. Avoid Keyword Stuffing.

Alt text is part of Image SEO, which also includes file names and surrounding text. The file name of an image also provides context; see Image File Name SEO for more. Note that the correct HTML attribute is alt, not 'alt tag'. The term 'alt tag' is a common misnomer.

Alt text is an on-page factor, unlike off-page signals such as backlinks. For more on off-page factors, see off page seo report. Also, alt text is different from Anchor Text, which describes linked text. For more on how file names affect SEO, see Image Filename SEO.

Common Alt Text Mistakes to Avoid

One common mistake is stuffing alt text with keywords. For example, writing 'cheap red shoes buy now best price' instead of 'Red running shoes on a track'. This hurts accessibility because screen readers read irrelevant text, and it may trigger spam filters. Another mistake is using vague fillers like 'image' or 'photo'. This provides no useful information to users or search engines.

Leaving alt text blank for informative images is another error. For instance, a photo of a historical monument should have alt text like 'Colosseum in Rome at sunset', not an empty attribute. Writing alt text that repeats the nearby caption is also wasteful. If the caption says 'Figure 1: Sales growth', the alt text should add detail, such as 'Line graph showing sales growth from 2019 to 2024, peaking in 2023'.

• Mistake: Stuffing alt text with keywords. Consequence: Hurts accessibility and may trigger spam filters.
• Mistake: Using vague fillers like 'image' or 'photo'. Consequence: Provides no useful information to users or search engines.
• Mistake: Leaving alt text blank for informative images. Consequence: Screen readers cannot convey the image's content, and search engines lose context.
• Mistake: Writing alt text that repeats the nearby caption. Consequence: Redundant and wastes an opportunity to add unique context.

Alt Text in Different Platforms

Adding alt text varies by platform. In WordPress, you enter it in the media library's 'Alt Text' field when uploading or editing an image. In Instagram, you can add alt text when creating a post by tapping 'Advanced Settings' and then 'Write Alt Text'. To see alt text on Instagram, go to a post, tap the three dots, and select 'View Alt Text'.

In Microsoft Word, right-click an image, choose 'Edit Alt Text', and type your description. Excel works similarly. For web developers, alt text is added directly in the HTML <img> tag. For more on how images appear in search, see Google Images Search Upload Photo.

Alt Text vs. Other Image Attributes

Images have several attributes that serve different purposes. Alt text is for accessibility and fallback. The title attribute provides additional information as a tooltip. Captions are visible text displayed below images. File names give search engines context but are not read by screen readers. Unlike a how meta description works which summarizes a page, alt text describes a single image. The following table compares these attributes.

Choose the right attribute for each need. Always prioritize alt text for accessibility.