Image SEO Best Practices: How to Rank Higher with Optimised Images

Why Image SEO Matters

Images are more than decoration. They're a significant source of organic search traffic and a crucial signal for Google's ranking algorithms:

• Google Images drives traffic. Google Images accounts for approximately 22% of all Google searches. If your images rank well, they can be a major traffic source.
• Images support E-E-A-T. Google's Experience, Expertise, Authoritativeness, and Trustworthiness (E-E-A-T) guidelines value original, helpful content — including unique, relevant images.
• Core Web Vitals are image-dependent. The Largest Contentful Paint (LCP) metric is often an image. Optimising images directly improves your CWV scores, which Google uses as a ranking signal.
• Visual search is growing. Google Lens processes billions of queries per year. Properly tagged and optimised images are more likely to appear in visual search results.

1. Write Descriptive, Useful Alt Text

The alt attribute is the single most important image SEO element. It serves three purposes:

1. Accessibility: Screen readers read alt text aloud to visually impaired users.
2. Context for search engines: Google uses alt text to understand what an image depicts, since it cannot "see" images the way humans do.
3. Fallback display: If an image fails to load, the browser displays the alt text instead.

Alt text best practices

• Be descriptive and specific. Instead of alt="image" or alt="photo", write alt="Golden retriever puppy playing in autumn leaves in a park".
• Include relevant keywords naturally. If the image is on a page about image compression, alt="Before and after comparison showing 65% file size reduction with lossy compression" is better than alt="comparison".
• Keep it under 125 characters. Most screen readers cut off alt text around 125 characters, so be concise but descriptive.
• Don't start with "Image of" or "Picture of". Screen readers already announce it as an image. Get straight to the description.
• Use empty alt for decorative images. If an image is purely decorative (background patterns, spacers), use alt="" to tell screen readers to skip it.

2. Use Descriptive File Names

Google reads file names as a signal for image content. Before uploading, rename your files from camera defaults to descriptive, keyword-rich names:

❌ Bad File Name	✅ Good File Name
IMG_20260215_143022.jpg	compressed-product-photo-before-after.jpg
screenshot-1.png	webp-conversion-settings-panel.png
DSC0001.jpeg	landscape-mountain-sunset-colorado.webp

Guidelines: Use hyphens to separate words (not underscores). Keep file names lowercase. Include the primary keyword for the image. Avoid keyword stuffing — keep it natural and accurate.

3. Optimise Image File Size

Page speed is a confirmed Google ranking factor. Large, uncompressed images are the number one cause of slow pages. Follow these rules:

• Compress all images before uploading. Use our Image Compressor to reduce file sizes by 40–80% without visible quality loss.
• Use WebP format for the best size-to-quality ratio. WebP images are 25–35% smaller than JPEG at equivalent visual quality. See our format comparison guide.
• Resize to display dimensions. Don't serve a 4000px-wide image when it's displayed at 800px. Use our Image Resizer to match image dimensions to their display size (2× for Retina).
• Target under 200 KB for most web images. Hero images can be up to 300 KB. Thumbnails should be under 50 KB.

4. Implement Responsive Images

Serving the same large image to both desktop and mobile users wastes bandwidth and hurts mobile rankings. Use the srcset attribute to provide multiple sizes:

<img srcset="product-400.webp 400w, product-800.webp 800w, product-1200.webp 1200w" sizes="(max-width: 640px) 400px, (max-width: 1024px) 800px, 1200px" src="product-800.webp" alt="Product photo showing compression quality">

This tells the browser to download only the size needed for the current viewport, potentially saving 60–80% of bandwidth on mobile devices.

5. Use Structured Data for Images

Schema.org structured data helps Google understand the context and content of your images. Key schema types for image SEO:

• ImageObject: Use this to provide detailed metadata about important images (name, description, content URL, dimensions, license).
• Product images: If you're selling products, include image URLs in your Product schema. This enables rich results in Google Shopping.
• Article images: Include an image property in your Article schema. Google uses this for rich snippets, Discover, and Top Stories.
• HowTo images: If you have step-by-step tutorials, include images for each step in your HowTo schema.

6. Create an Image Sitemap

An image sitemap helps Google discover images that it might not find through normal crawling — especially images loaded via JavaScript, CSS, or lazy loading. You can either create a dedicated image sitemap or add image information to your existing sitemap:

<url><loc>https://example.com/page</loc><image:image><image:loc>https://example.com/images/photo.webp</image:loc><image:title>Descriptive title</image:title></image:image></url>

7. Add Proper Image Dimensions

Always include width and height attributes on your <img> tags. This prevents Cumulative Layout Shift (CLS) — a Core Web Vitals metric that measures visual stability. Without explicit dimensions, the browser doesn't know how much space to reserve, causing the page to "jump" when the image loads.

8. Use Lazy Loading Strategically

Add loading="lazy" to off-screen images so they load only when the user scrolls near them. This improves initial page load speed. However:

• Never lazy-load the LCP image. Your hero image or first visible image should load eagerly with fetchpriority="high".
• Don't lazy-load above-the-fold images. Any image visible without scrolling should load immediately.

9. Optimise Image Captions and Surrounding Text

Google uses the text surrounding an image to better understand its content. Place images near relevant text that describes or references them. Use descriptive captions when appropriate — they increase user engagement and provide additional SEO context.

10. Use Original Images When Possible

Google's algorithms favour original images over stock photos. Original images support E-E-A-T signals and are more likely to rank in Google Images. When you must use stock photos, add significant value through editing, annotation, or context.

Image SEO Checklist

1. ✅ Descriptive, keyword-rich alt text (under 125 characters)
2. ✅ Descriptive file names with hyphens (not underscores)
3. ✅ Compressed to under 200 KB (use our compressor)
4. ✅ WebP format for best performance
5. ✅ Resized to display dimensions (2× for Retina)
6. ✅ Responsive images with srcset
7. ✅ Explicit width and height attributes
8. ✅ Lazy loading for off-screen images
9. ✅ Structured data (ImageObject or Article schema)
10. ✅ Image sitemap submitted to Google Search Console
11. ✅ Original images when possible
12. ✅ Descriptive captions and surrounding context

Start Optimising Your Images

The best image SEO starts with properly compressed, correctly formatted images. Use our free image tools to compress, convert, resize, and batch process your images — then apply the SEO best practices above to maximise your organic traffic.