The Ultimate Guide to Website Image Sizes: How to Balance Quality, Speed, and SEO
Ever landed on a website that took forever to load… or where the images looked fuzzy and stretched?
That’s what happens when image sizes aren’t optimised.
With over 60% of web traffic now coming from mobile devices (Statista, 2024), getting your image dimensions right isn’t just about looks — it’s about speed, SEO, and conversions.
Poorly sized or oversized images slow down your site, frustrate visitors, and push your Google rankings down. But when you get it right, your website looks sharp, loads fast, and keeps visitors engaged longer — all things Google loves.
This guide will show you exactly how to choose the right image sizes, compress files without losing quality, and improve both user experience and SEO performance.
Key Takeaways
Speed is everything. Proper image sizing improves page speed — a key SEO ranking factor.
Consistency counts. Uniform image dimensions keep your design looking professional.
Compress smartly. Reduce file size without losing visual clarity.
Pick the right format. WebP or AVIF outperform PNG and JPEG for modern web performance.
Always use alt text. It’s a quick SEO and accessibility win.
Why Image Size Matters More Than You Think
According to Google, a one-second delay in page load time can cut conversions by up to 20%.
That’s huge.
Large, unoptimised images are one of the main reasons websites load slowly. This directly affects:
User experience: Visitors expect fast, smooth pages.
SEO: Google rewards fast-loading websites.
Conversions: Faster sites mean lower bounce rates and more sales or enquiries.
If you’re serious about improving site performance, this is just as important as your Google Ads strategy or SEO setup.
The Best Image Sizes for Websites
Here’s a quick reference guide for optimal image dimensions across desktop and mobile:
| Image Type | Desktop (W x H) | Mobile (W x H) | Aspect Ratio |
|---|---|---|---|
| Background image | 2560 × 1400 px | 640 × 360 px | 16:9 |
| Hero image | 1920 × 1080 px | 640 × 360 px | 16:9 |
| Website banner | 1200 × 400 px | 360 × 120 px | 3:1 |
| Blog image | 1200 × 800 px | 360 × 240 px | 3:2 |
| Logo (rectangle) | 400 × 100 px | 160 × 40 px | 4:1 |
| Logo (square) | 100 × 100 px | 60 × 60 px | 1:1 |
| Favicon | 16 × 16 px | 16 × 16 px | 1:1 |
| Thumbnail / Product | 300 × 300 px | 150 × 150 px | 1:1 |
💡 Pro Tip: Upload at slightly higher resolution than your display size — it keeps your site crisp on Retina and 4K screens without slowing it down.
How to Optimise Website Images Like a Pro
1. Choose Consistent Dimensions
Nothing ruins a website’s flow faster than mismatched image sizes.
Stick to standard aspect ratios:
Square (1:1) for products and thumbnails.
Landscape (16:9) for hero sections or banners.
3:2 for blog and article headers.
A consistent layout builds trust and looks professional — especially important for local SEO campaigns and landing pages designed to convert.
2. Compress Without Sacrificing Quality
Every kilobyte matters. Aim to keep most images under 500 KB (ideally between 150–300 KB).
Use compression tools like:
TinyPNG – Shrinks PNG and JPEGs while preserving detail.
Squoosh by Google – Free and incredibly effective.
ImageOptim – Mac favourite for batch compression.
These tools can reduce file size by up to 80% — which could shave seconds off your page load time.
3. Pick the Right File Type
Each file format serves a different purpose:
| Format | Best For | Why It Matters |
|---|---|---|
| WebP | All-purpose images | 30% smaller than JPEGs, great quality |
| JPEG | Photos | Small, widely supported |
| PNG | Transparent backgrounds | Lossless quality |
| SVG | Logos and icons | Scales infinitely without losing clarity |
| AVIF | Performance-focused sites | Ultra-efficient, modern compression |
💡 Above Digital Tip: If your site uses a CDN (like Cloudflare), it can automatically serve the best format for each browser.
4. Write SEO-Friendly Alt Text
Alt text tells Google and screen readers what your image represents.
It’s essential for accessibility and SEO.
Example:
✅ “Gold Coast plumber installing new sink”
❌ “plumber123.jpg”
Keep it under 100 characters, and include relevant keywords naturally.
For more SEO insights, check out our guide: SEO for Tradies: How to Rank Locally.
5. Make Your Images Responsive
Your website should adapt to every screen size automatically.
If your platform doesn’t do this natively, use responsive design techniques or tools like Cloudflare Images or Imgix.
Responsive design ensures your website looks clean, loads faster, and passes Google’s Core Web Vitals benchmarks.
Common Image Mistakes (and Fixes)
| Issue | Why It Happens | Quick Fix |
|---|---|---|
| Slow loading | Oversized files | Compress and convert to WebP |
| Blurry visuals | Image too small | Upload higher-resolution source |
| Broken links | Incorrect file path | Check file URLs carefully |
| Layout distortion | Wrong aspect ratio | Crop or resize evenly |
| Poor SEO | Missing alt text | Add keyword-rich alt tags |
If your site is still struggling with speed, run it through Google PageSpeed Insights — it’ll pinpoint which images are slowing you down.
Our Favourite Image Optimisation Tools
Here are a few free and reliable tools we recommend:
TinyPNG – Perfect for compressing product and hero images.
Squoosh – Google’s lightweight web app.
Canva – Resize for social, blog, or banner use.
Photoshop “Save for Web” – For precise control over file quality.
The Bottom Line
Optimising your image sizes isn’t about being pixel-perfect — it’s about performance and perception.
Fast-loading, high-quality visuals make your brand look professional, improve SEO, and enhance the user experience — especially on mobile.
So before uploading your next image, ask:
“Will this make my site faster or slower?”
If your goal is to attract, engage, and convert — faster pages and sharper visuals are a no-brainer.
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