How to Optimize Images for Website SEO (Free Checklist)
How to Optimize Images for Website SEO (Free Checklist)
Images are the heaviest files on most pages — and the most ignored. A single unoptimized photo can double your load time, hurt Core Web Vitals, and push rankings down. Here's a practical checklist to fix every image on your site, free, in minutes.
Why image size matters for SEO
- Load speed is a confirmed ranking factor. Heavy images slow pages, increase bounce rate, and signal low quality.
- Google Images is a traffic channel: optimized images with good alt text rank independently.
- Core Web Vitals score is directly dragged down by large LCP images — the hero image is the first thing a visitor waits for.
The 5-step image optimization checklist
1. Resize to the display size
Never upload a 6000px photo that displays at 800px. Resize to the largest width it will ever show. Use our Resize Image tool — blog images at 1200px, hero images at 1600-2000px, thumbnails at 300-400px.
2. Convert to WebP
WebP is 25-35% smaller than JPG at identical quality and every modern browser supports it. Convert with the JPG to WebP or PNG to WebP converters.
3. Compress the file
Target under 150-300KB for content images and under 1MB for heroes. The Compress Image tool shows live sizes as you drag the quality slider — aim for 70-80% on photos.
4. Keep transparency only when needed
Use PNG or WebP only where transparency is essential — logos, icons, cutouts. Otherwise JPG/WebP at high compression is undetectable and much faster.
5. Write descriptive alt text
Describe the image plainly, in one sentence, with the keyword where natural. "Compressed WebP hero of a mountain at sunset, 1200px wide" beats "img_4832".
Quick wins this week
- Start with your LCP image — usually the hero. Resize + compress it and watch your page speed improve immediately.
- Batch old content: reuse Image to PDF or compress pages to standardize legacy uploads.
- Check your biggest files once a month — images drift back over time.
The formula: Resize first → convert to WebP → compress to under 300KB → describe with alt text. Skip one step and you're leaving traffic and speed on the table.