What is the ideal length for image alt text?

Alt text should be 80 to 125 characters long - descriptive enough to convey the image's content and context, but concise enough that screen readers can deliver it smoothly. Avoid keyword stuffing. Write alt text as a natural description of what the image shows and why it matters in the context of the surrounding content.

Does alt text affect Google search rankings?

Alt text directly affects Google Image Search rankings and indirectly supports overall page SEO. Google uses alt text as the primary signal for understanding what an image depicts. Pages with descriptive, relevant alt text on images rank better in image search and provide additional context signals that help Google understand the page's overall topic.

Should every image have alt text?

Every content image should have descriptive alt text. Decorative images like background patterns, dividers, and spacer images should use an empty alt attribute to tell screen readers to skip them. If an image conveys information or context that matters for understanding the content, it needs meaningful alt text. If it is purely visual decoration, leave the alt attribute empty.

What Is Image Alt Text for SEO?

Image alt text (alternative text) is a written description added to an image's HTML code that serves two primary purposes: it makes images accessible to visually impaired users who rely on screen readers, and it helps search engines understand what an image depicts. According to WebAIM's annual accessibility survey, missing or inadequate alt text is the second most common accessibility error on the web, appearing on 55% of home pages analyzed. For SEO, alt text is the primary signal Google uses to index and rank images in Google Image Search, which drives approximately 22% of all Google searches.

How Does Alt Text Work?

In HTML, alt text is added to images using the alt attribute within the <img> tag:

<img src="social-media-dashboard.png" alt="Social media analytics dashboard showing engagement metrics across Instagram, TikTok, and LinkedIn">

When a screen reader encounters this image, it reads the alt text aloud to the user. When Google's crawler encounters it, it uses the alt text to understand the image's content and context. If the image fails to load, the browser displays the alt text in place of the image.

The alt text should describe what the image shows in a way that makes sense in the context of the surrounding content. It should be specific enough to be useful but concise enough to not disrupt the reading flow - typically 80 to 125 characters.

What Makes Good Alt Text for SEO?

Be descriptive and specific. "Chart" is bad alt text. "Bar chart showing monthly organic traffic growth from 1,000 to 15,000 visits over 12 months" is good alt text. The specific description tells both screen readers and search engines exactly what the image communicates.

Include relevant keywords naturally. If the image shows a social media management dashboard, use that phrase in the alt text. But do not stuff keywords unnaturally - "social media management tool best social media software social media dashboard" is spam. Write the description you would give someone who cannot see the image, and let keywords appear naturally.

Describe the context, not just the visual. An image of a person typing on a laptop could be described as "person using laptop" or "marketing manager creating social media content calendar in scheduling tool." The second version provides context that connects the image to the page's topic and adds SEO relevance.

Skip "image of" and "photo of." Screen readers already announce that an element is an image, so starting with "image of" or "photo of" is redundant. Start directly with the description.

How Do Search Engines Use Alt Text?

Google's image search relies heavily on alt text because search engines cannot "see" images the way humans do. While Google's vision AI has improved significantly, alt text remains the primary explicit signal for image understanding. Google's SEO documentation specifically states that alt text helps Google understand the subject matter of an image and how it relates to the page's content.

Beyond image search, alt text provides contextual signals for the overall page. A page about content marketing with images that have relevant alt text reinforces the page's topical focus. This supporting signal is subtle but contributes to the page's overall relevance score for related queries.

Alt text also affects Google's featured snippets and AI Overviews. When Google includes an image in a SERP feature, it uses the alt text to determine which image best matches the query. Descriptive alt text increases the chance your images appear in these prominent SERP positions.

How Do AI Models Interpret Alt Text?

This is an increasingly important consideration. AI search engines like ChatGPT, Perplexity, and Google's AI Overviews use alt text as part of their content understanding when crawling pages. Well-written alt text helps AI models build a more complete picture of your page's content, which can influence whether your page gets cited in AI-generated responses.

AI models that crawl the web read both the visible text and the HTML metadata, including alt text. An image with descriptive alt text gives the AI model additional context about the page's topic that supports the main content. While alt text alone will not determine AI citations, it contributes to the overall content quality signal that AI models evaluate.

What Are Common Alt Text Mistakes?

Leaving alt text empty on content images. This is the most common error and hurts both accessibility and SEO. Every image that conveys meaning needs descriptive alt text.

Keyword stuffing. Writing alt text like "best SEO tool SEO software SEO platform" is spam. Google recognizes keyword stuffing in alt text and it can actually hurt your rankings rather than help them.

Using file names as alt text. "IMG_4532.jpg" or "screenshot-2026-02-27.png" tells no one anything useful. Write proper descriptions.

Writing the same alt text for multiple images. Each image on a page should have unique alt text that describes that specific image. Duplicating alt text across images wastes an opportunity to provide additional context signals.

For startups building content at scale, creating a simple alt text guide for your team - describing format, length, and examples of good versus bad alt text - prevents these mistakes and ensures consistent quality across all published content.