Image SEO Analyzer

Every image, checked

Enter a URL and we load the page in a real Chrome browser and inspect every image that ends up on it, including ones added by JavaScript. For each one we measure the file size, its real dimensions against the size it’s shown at, its format, and whether it’s in the first screenful. It flags:

• Missing alt text, and alt text that’s too short (under 5 characters) or too long (over 125).
• Large files: over 500 KB anywhere, or over 200 KB in the first screen.
• Oversized images: much bigger than the space they’re shown in.
• Large images without srcset, so phones download the desktop version.
• Lazy loading mistakes: images below the fold that aren’t lazy, and images up top that are.
• Older formats: JPG, PNG and GIF where WebP or AVIF would be smaller.

The summary totals it all up: images with and without alt text, lazy loading, srcset, oversized images, modern and older formats, and total image weight.

Why images matter for SEO

Images are usually the heaviest part of a page, and the biggest one in the first screen is often the Largest Contentful Paint, one of Google’s Core Web Vitals. Unoptimized images are the single most common reason pages are slow on mobile.

They’re content, too. Good alt text tells search engines what an image shows, helps it appear in Google Images, and makes the page usable with a screen reader. For product, recipe and travel sites, image search can bring real traffic.

Fixing the usual problems

Missing or weak alt text

Describe what the image shows and why it’s there: “Red trail running shoe with a thick cushioned sole, side view”, not “shoe” or “IMG_4821”. Keep it under about 125 characters and skip the keyword stuffing.

Big files

Compress before uploading, or let your CMS or image CDN do it. Photo quality around 75 to 85 usually looks identical at a fraction of the size. Aim to keep the hero image under about 100 to 200 KB.

Oversized images

A 4000-pixel photo in a 400-pixel slot makes visitors download ten times more pixels than they can see. Resize to the largest size it’s shown at, and use srcset so each device gets the right one:

<img
  src="/shoe-800.webp"
  srcset="/shoe-400.webp 400w, /shoe-800.webp 800w, /shoe-1600.webp 1600w"
  sizes="(max-width: 600px) 100vw, 400px"
  width="800" height="600"
  alt="Red trail running shoe, side view">

Lazy loading

Add loading="lazy" to images below the fold so they only load as the visitor scrolls near them.

Formats

WebP works in every modern browser and is typically 25 to 35 percent smaller than the same JPG. AVIF is often smaller still. Use SVG for logos and icons. Many platforms convert automatically, so check yours before doing it by hand.

Width and height

Always set width and height, or a CSS aspect ratio, so the browser saves space before the image arrives. Otherwise the layout jumps.

Image SEO checklist

1. Descriptive file names, like red-trail-running-shoe.webp.
2. Real alt text on content images, empty alt on decorative ones.
3. Resized to display size and compressed.
4. WebP or AVIF, with responsive srcset.
5. Lazy below the fold, eager for the hero.
6. Dimensions set to stop layout shift.
7. Important images in <img> tags, not just CSS backgrounds, which aren’t indexed as images.

Quick answers

Why does this tool render JavaScript?

Sliders, galleries and lazy loading libraries often add images with JavaScript. A plain HTML check would miss them, or only see placeholders.

Does alt text need my keyword?

Only if it naturally describes the image. Accurate descriptions help image search and accessibility; forced keywords help neither.