Google Image Search drives 20–30% of total organic traffic for many sites — sometimes more for ecommerce, recipes, and how-to content. Most teams optimize text relentlessly and treat images as decoration. The result is leaving easy ranking wins on the table. This is the full checklist we run on every site we audit.

1. Use descriptive, keyword-rich filenames

Google reads the filename as a relevance signal. IMG_4521.jpg tells the crawler nothing. red-leather-running-shoe-side-view.jpg tells it the entire subject. Rename before upload. Use dashes, not underscores — Google has stated dashes are treated as word separators, underscores aren't.

2. Write meaningful alt text — but don't keyword-stuff

Alt text serves two audiences: screen readers and search engines. The same rule works for both: describe the image accurately. alt="Red leather running shoe with white sole, side view" is good. alt="running shoe red leather running shoe buy running shoe online" is keyword stuffing and Google detects it.

Decorative images (icons, dividers) should have alt="" — empty, not omitted. Empty alt tells screen readers to skip the image.

3. Match the displayed dimensions to the file dimensions

Serving a 4032×3024 photo into a 600×450 slot wastes 95% of the bytes. The browser downloads the full image, scales it down on render, and the visual result is identical. Resize before upload, or use srcset to serve multiple variants.

Lighthouse's "Properly size images" audit catches this. So does Google's mobile-friendly rank signal.

4. Use modern formats with fallbacks

WebP saves 25–35% bytes versus JPEG/PNG. AVIF saves another 20% on top. Both ship to 95%+ of users in 2026. Use <picture> to serve modern formats with safe fallbacks:

<picture> <source type="image/avif" srcset="hero.avif"> <source type="image/webp" srcset="hero.webp"> <img src="hero.jpg" alt="..."> </picture>

5. Lazy-load below-the-fold images

The loading="lazy" attribute on <img> tells the browser to defer download until the image is near the viewport. This is one line per image and frees bandwidth for the LCP element. Don't lazy-load above-the-fold images — that delays LCP.

6. Set explicit width and height

Without dimensions on <img>, the browser doesn't reserve space for the image until it loads. The page's content jumps when each image arrives — bad for Cumulative Layout Shift, the C in Core Web Vitals. Always set width and height (or aspect-ratio in CSS).

7. Compress aggressively

For photos: JPEG quality 80, WebP quality 80, AVIF quality 60. These are imperceptible from the source but shed 50–70% of bytes versus the camera output. For UI screenshots and graphics: WebP lossless. Bulk compression tools like our Image Compressor handle this in batches, in the browser, with no upload.

8. Use the structured-data ImageObject schema

Adding <script type="application/ld+json"> with an ImageObject entry attached to product pages, articles, and recipes helps Google show your image in rich results. Required fields:

contentUrl — the image URL
creator — author
license — license URL (especially valuable for stock photo SEO)
caption — short description

9. Make images crawlable

Two ways images get hidden from Google:

JavaScript-only loading. If the image is added by JS after the page loads (and there's no <noscript> fallback), Googlebot may miss it. Server-render or pre-render the <img> tag.
CSS background images on content. Google treats them as decorative. For meaningful images, use <img>, not background-image.

10. Submit an image sitemap

Add image entries to your XML sitemap. The format:

<url> <loc>https://example.com/page</loc> <image:image> <image:loc>https://example.com/image.jpg</image:loc> </image:image> </url>

Especially valuable for sites with images that load dynamically (image galleries, product catalogs).

11. Optimize for image search intent, not page intent

A "running shoes" page might rank #4 in web search but #1 in image search if the imagery is clearer. Image search users have different intent — they're often shopping or researching. The image needs to stand alone:

Show the product clearly, on a clean background
Don't put text over the image (Google reads the image, not the overlay)
Show context where it adds clarity (a shoe on a foot, not just on white)

12. Don't lose EXIF metadata you actually want

Some compressors strip all EXIF on optimization. For photography portfolios, this kills the camera/lens metadata that helps the page rank for camera-specific queries ("Sony A7R5 sample images"). Configure your compressor to preserve EXIF, or use a tool that lets you choose.

For non-photography sites, stripping EXIF is fine — it shrinks the file and removes location data you probably don't want to publish.

The audit, in 60 seconds

Open any page on your site. In DevTools Network panel, filter to "Img". For each image:

Filename describes the subject? ✓
File size < 200 KB for non-hero images? ✓
Format is WebP or AVIF? ✓
Dimensions match displayed size (within 2x)? ✓
Has descriptive alt text? ✓
Has explicit width/height attributes? ✓
Below-the-fold has loading="lazy"? ✓

Most sites we audit fail four or five of those on the first page they show us. Fixing them is a small change with compounding returns — every image fix benefits every page view that loads it, and image search rewards the cleanup with traffic.