Google Can't See Your Images. Alt Text Is How It "Reads" Them.
You uploaded a beautiful infographic.
It has no alt text.
To Google, it doesn't exist.
What Alt Text Should Do
Describe the image accurately. Include your keyword naturally (when it fits). Provide context for visually impaired users.
That's it. Not complicated.
Examples
Bad: alt="image1" or alt="" or no alt text at all.
Mediocre: alt="SEO checklist"
Good: alt="On-page SEO checklist showing 15 optimization tasks organized by priority"
Descriptive. Natural. Useful.
Common Mistakes
Keyword stuffing the alt text. "SEO checklist best SEO checklist free SEO checklist download" -- don't. That's the same keyword density myth that kills body copy, applied to images.
Using the same alt text on every image. Each image is different. Each alt text should be too.
Skipping it entirely. The most common mistake. And the easiest to fix. For the full picture on image optimization for SEO, we go much deeper there.
Google's SEO starter guide specifically covers image best practices, including alt text.
Track this with SEO Checkup. 113 tasks including image optimization. Free. 30 seconds.