Image Optimisation, explained properly.
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 is WordPress, Shopify or Squarespace, without a full image audit and optimisation pass. When images are bloated, blurry or broken, users bounce, and Google notices.
Why image optimisation matters for SEO
- **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
1. **Resize images** before uploading, do not let your CMS scale them on the fly. 2. **Compress images** using tools like TinyPNG or ShortPixel. 3. **Use next-gen formats** like WebP where supported. 4. **Add descriptive alt text** for SEO and accessibility. 5. **Use descriptive filenames** (not IMG00123.jpg), for example seo-glossary-image-optimisation.webp. 6. **Lazy load images** to defer off-screen content. 7. **Serve images via CDN** if you have global traffic.
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:** 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 favour 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 is not visible to most users, but it is 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 is a key ranking booster on our SEO Blueprint course too.
How to optimise images in WordPress
Our preferred WordPress stack for image SEO and performance: - **ShortPixel or Imagify:** compression and WebP conversion. - **Bricks Builder:** precise control over image rendering. - **Rank Math:** audit missing alt text and filenames. - **Native lazy loading:** built into WordPress as of version 5.5+. Tools like Squoosh let you optimise images before uploading, ideal for ecommerce and media-heavy sites.
Common image SEO mistakes
- Uploading 3MB+ hero images - No alt text, or 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 Every one of these 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 mean higher conversions, and better alt text means 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 use 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.
Image Optimisation: common 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 is not practical. PNG only when transparency or pixel-perfect graphics are needed. SVG for icons and simple illustrations. Avoid GIF for photos; it is 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 and include the focus keyword where natural. Do not 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.
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