TL;DR: Preparing images so they load fast and help SEO without losing quality.
In a nutshell
Image optimisation covers choosing the right format (usually WebP), compressing file size, writing descriptive alt text and filenames, and lazy-loading off-screen images. For example, swapping a 3MB hero JPEG for a 150KB WebP can cut Largest Contentful Paint by seconds, lift Core Web Vitals, and free up image-search traffic the page was missing.
Quick answer: Image optimisation is the practice of preparing images for the web in ways that lift SEO and improve user experience: appropriate file format, compressed file size, descriptive alt text, meaningful file names, and responsive sizing. Done properly, image optimisation lifts page speed, supports image search rankings, and improves accessibility, all from one set of decisions.
What Is Image Optimisation?
Image optimisation is the process of making your images work harder for SEO, site speed, and accessibility. That means reducing file sizes, using the right formats, writing descriptive alt text, and making sure images load quickly and clearly on all devices.
Done right, image optimisation can speed up your website, improve Core Web Vitals, boost rankings in image search, and make your content more engaging and accessible to all users.
At BrisTechTonic, we never ship a site, whether it’s WordPress, Shopify, or Squarespace, without a full image audit and optimisation pass. Because when images are bloated, blurry or broken… users bounce. And Google notices.
Why Image Optimisation Matters for SEO
Let’s break it down:
- Faster load times: Optimised images reduce page weight, helping your page speed.
- Better UX: Sharp, quick-loading visuals improve the user experience.
- Improved rankings: Google uses speed and accessibility as ranking factors.
- Image search visibility: Alt text and filenames help your images show up in Google Images (a hidden traffic gem!).
- Accessibility: Screen readers rely on alt text to describe visuals to visually impaired users.
Image Optimisation Checklist
Here’s the BrisTechTonic approach to image optimisation:
- Resize images before uploading, don’t let your CMS scale them down on the fly.
- Compress images using tools like TinyPNG or ShortPixel.
- Use next-gen formats like WebP where supported.
- Add descriptive alt text for SEO and accessibility.
- Use descriptive filenames (not
IMG00123.jpg), e.g.seo-glossary-image-optimisation.webp. - Lazy load images to defer off-screen content (see Lazy Loading).
- Serve images via CDN if you’ve got global traffic.
If you’ve ever seen a beautiful, fast site and wondered what makes it feel slick, optimised images are probably part of the secret sauce.
Image Formats: What to Use (and When)
- JPG/JPEG: Great for photos. Small file sizes, decent quality.
- PNG: Best for transparency. Larger files, but sharper edges.
- WebP: The future. Small file size, great quality. Supported by most modern browsers.
- SVG: Perfect for logos, icons, and simple graphics, scalable and razor-sharp.
At BrisTechTonic, we love WebP, especially for WordPress sites using tools like ShortPixel or Imagify to convert automatically on upload.
Alt Text: Your Secret SEO Weapon
Alt text describes what an image shows. It’s not visible to most users, but it’s critical for:
- Accessibility (screen readers rely on it)
- SEO (Google reads it like page copy)
- Image search rankings
Example of bad alt text: image123
Example of good alt text: Optimised image of SEO report on laptop screen
We optimise alt tags across every SEO audit, and it’s a key ranking booster on our SEO Blueprint course too. For the underlying HTML, see our ALT attribute entry.
How to Optimise Images in WordPress
Here’s our preferred WordPress stack for image SEO and performance:
- ShortPixel or Imagify: Compression + WebP conversion
- Bricks Builder: Gives precise control over image rendering
- Rank Math: Lets you audit missing alt text and filenames
- Native lazy loading: Built into WordPress as of version 5.5+
Bonus: Tools like Squoosh let you optimise images before uploading, ideal for ecommerce and media-heavy sites.
Common Image SEO Mistakes
These are the red flags we find in nearly every audit:
- Uploading 3MB+ hero images (!)
- No alt text, or worse, the same alt on every image
- Using “image.jpg” or “screenshot_2023_01.png” filenames
- Forgetting to use lazy loading
- Images not scaling properly on mobile (see responsive design)
Every one of these issues is fixable, and most have a direct impact on traffic and conversions.
Image Optimisation and Ecommerce
Product-heavy sites like Shopify and WooCommerce stores benefit massively from optimised images. Faster loads = higher conversions. Better alt text = stronger rankings in product searches and image SERPs.
We include image optimisation in all our Ecommerce SEO work and website redesigns, because it can make or break a product page’s success.
Image SEO and Structured Data
If you’re using schema markup (like Product, Article, or FAQPage), images can be included in your schema for richer results.
This is especially powerful for guides, blogs, and reviews, and something we cover in our Consultant Bootcamp course.
External Resources
Frequently Asked Questions
What image format should I use for SEO?
WebP for most modern web use cases (smaller files than JPEG with comparable quality). JPEG for photos when WebP isn’t practical. PNG only when transparency or pixel-perfect graphics are needed. SVG for icons and simple illustrations. Avoid GIF for photos; it’s only appropriate for short looping animations.
How small should my image files be?
Hero images: under 200KB ideally. Body images: under 100KB ideally. Thumbnails: under 30KB. Larger files slow page load and damage Core Web Vitals. Tools like TinyPNG, ImageOptim, and Squoosh compress images without visible quality loss.
What should image filenames include?
Descriptive words rather than camera defaults. running-shoes-mens-black.jpg beats IMG_3942.jpg. Match the filename to what the image actually shows; include the focus keyword where natural. Don’t over-engineer; descriptive natural filenames are enough.
How do I optimise images for accessibility?
Alt text describing what the image shows is the primary signal. Decorative images use empty alt text (alt=""). Complex images (charts, infographics) benefit from longer descriptions in surrounding text. Captions can supplement alt text where visual context helps understanding.
Take this further
Image optimisation is technical SEO that pays back across speed, accessibility, and image search. We treat it as a foundational discipline.
Ready to apply this to your own site? Book a free discovery call, or explore our SEO strategy service.