Your Beautiful Hero Image Is a 4MB Anchor Dragging Your Site to the Bottom of the Ocean
Hear me when I say this.
Images are usually the single biggest contributor to page weight. And page weight is the single easiest thing to fix. According to the HTTP Archive, images account for nearly half of the average page's total bytes.
Yet here we are. In 2026. Still serving uncompressed PNGs to mobile users on 3G connections.
sighs
The Format Hierarchy
AVIF — best compression, best quality. Use it if browser support works for your audience.
WebP — excellent compression, nearly universal support. This should be your default.
JPEG — the fallback. Still fine for photos. Use quality 75-85.
PNG — only for images that need transparency. And even then, consider WebP with alpha.
SVG — for icons, logos, simple illustrations. Infinitely scalable. Tiny file size.
Sizing Matters More Than Format
Serving a 3000px wide image to a 375px wide phone screen is insane. Yet it happens on most websites.
Use responsive images. The `srcset` attribute exists for this exact reason. Serve the right size to the right device.
A 400px wide image for mobile. 800px for tablet. 1200px for desktop. Not one 3000px image for everyone.
Alt Text Is Not Optional
Every image needs descriptive alt text. Not "image1.jpg." Not "photo." A real description that tells search engines (and screen readers) what the image shows.
"Red running shoes on a white background" beats "shoes" every single time. Alt text is also covered in our on-page SEO checklist.
Lazy Loading: Do It
Images below the fold should use `loading="lazy"`. The browser will not fetch them until the user scrolls near them. Free performance win.
But do NOT lazy-load your LCP image. That hero image at the top? Load it immediately. Preload it, even. We explain why in our LCP fix guide. And if you want to dig into lazy loading specifically, read our lazy loading post.
The Checklist Approach
Image optimization has a dozen moving parts. Formats, sizes, alt text, lazy loading, compression, CDN delivery...
Track all of it. seocheckup.app covers image optimization as part of our 113-task checklist. Free. No credit card. 30 seconds.
Stop guessing which images are slowing you down.