Alt Text
Descriptive text added to an image's HTML alt attribute that tells search engines and screen readers what the image depicts — improving image SEO, accessibility, and page relevance signals.
Simple Explanation
Alt text (short for alternative text) is a description you add to images that tells both search engines and visually impaired users what an image shows. In HTML it looks like: <img src='image.jpg' alt='SEO audit tool showing a page score of 85'>. Google can't see images the way humans do — it reads the alt text to understand what an image contains. Good alt text describes the image accurately, includes relevant keywords where natural, and helps your images appear in Google Image search. It's also an accessibility requirement — screen readers read alt text aloud to blind users.
Advanced SEO Explanation
Alt text serves two distinct SEO functions: image indexing and page relevance. For image indexing, Google uses alt text as the primary signal for what an image depicts — affecting visibility in Google Images (a significant traffic source for visual niches). For page relevance, alt text adds to the semantic keyword signals on the page — an image of a 'canonical tag implementation diagram' with appropriate alt text reinforces the page's relevance for canonical tag queries. Image file names also matter: 'canonical-tag-example.png' ranks better than 'IMG_4921.png.' Best practices: describe the image accurately and specifically, include the target keyword naturally (not stuffed), keep alt text under 125 characters (screen reader limit), leave alt text empty (alt='') for purely decorative images that add no informational value.
Why Alt Text Matters for Rankings
Google Images traffic opportunity
Pages with well-optimized alt text rank in Google Images, providing an additional traffic channel beyond standard organic search.
On-page keyword reinforcement
Alt text adds relevant keyword signals to a page without adding visible text — reinforcing topical relevance for the page's target queries.
Accessibility compliance
Missing alt text on informational images violates WCAG accessibility guidelines. Google's quality systems reward accessible pages.
Fallback when images don't load
When images fail to load, alt text displays in their place — maintaining content comprehension and user experience.
Real-World SEO Examples
Good vs bad alt text
The spectrum from missing to over-optimized alt text.
alt="" (missing on an informational image) alt="image" (useless description) alt="seo audit tool free seo checker keyword density canonical tag" (keyword stuffing)
alt="SEO audit results showing title tag score of 85 out of 100" alt="Canonical tag implementation in HTML head section" alt="Before and after: duplicate content resolved with canonical tag" → Describes the actual image, includes relevant keyword naturally
Alt text HTML syntax
Correct implementation with good and bad examples.
Code Example
<!-- Informational image — descriptive alt text required -->
<img src="seo-audit-results.png"
alt="SEO audit results showing title tag, meta description, and heading structure scores" />
<!-- Decorative image — empty alt attribute (correct!) -->
<img src="decorative-divider.png" alt="" />
<!-- Image with keyword naturally included -->
<img src="canonical-tag-example.png"
alt="HTML code showing canonical tag implementation in page head" />Common Alt Text Mistakes
✗ Mistake
Missing alt text on all images
✓ The Fix
Add descriptive alt text to every informational image. Use empty alt='' for purely decorative images. Missing alt text on informational images is both an SEO and accessibility failure.
✗ Mistake
Using file name as alt text
✓ The Fix
Alt text should describe the image content, not repeat the file name. 'IMG_4921.jpg' as alt text is worse than no alt text.
✗ Mistake
Keyword-stuffing alt text
✓ The Fix
Include the relevant keyword once if natural. Stuffing multiple keywords into alt text is a spam signal. 'Free SEO audit tool best keyword checker alt text generator' is clearly manipulative.
✗ Mistake
Identical alt text on multiple images
✓ The Fix
Each image should have unique alt text that describes that specific image. Duplicate alt text provides no additional keyword signal and signals low quality.
Free Tools for Alt Text
Related Articles
Alt Text FAQs
Frequently Asked Questions
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Continue Learning: Next Terms
Keyword Density
The percentage of times a target keyword appears in a piece of content relative to total word count — a basic content signal that's often misunderstood and misapplied.
Beginner🔑Keyword Stuffing
The black-hat SEO practice of overloading content with keywords to manipulate rankings — a spam technique that Google actively penalizes with ranking suppression.
Beginner📄Heading Tags
HTML elements (H1 through H6) that create hierarchical content structure on a page, signaling topic organization to both readers and search engines.
Beginner📄Thin Content
Web pages with little to no unique value — minimal text, auto-generated content, affiliate pages with no original analysis, or pages that fail to satisfy user search intent.
Beginner