How to Optimize Images for a Faster Website
Large images are the number one cause of slow sites. Here is how to cut image weight by 60 to 80 percent without visible quality loss.
Reviewed by Jacob Rhinehart for Strelva's co-founder; products and operations lead responsibilities.
Unoptimized images are the single biggest cause of slow websites. On most sites they account for the majority of total page weight. The good news is that this is also the easiest performance problem to fix: you can usually cut image weight by 60 to 80 percent with no visible quality loss.
Why image weight matters
Every oversized image delays your page, hurts your LCP, and burns mobile data for visitors on slower connections. Lighter images mean faster loads, better Core Web Vitals, and higher conversion rates, especially on phones.
How to optimize them
- Find your largest images. Use PageSpeed Insights or your browser's network tab to see which images weigh the most. Fix the heaviest first.
- Choose the right format. Use WebP or AVIF for photos, SVG for logos and icons, and PNG only when you truly need transparency. Modern formats are dramatically smaller than old JPEGs and PNGs.
- Resize to the real display size. A 4000-pixel-wide photo shown in a 800-pixel slot is wasted weight. Export images at no more than twice their display size.
- Compress. Run images through a tool like Squoosh and reduce quality until just before you can see a difference. The savings are large and invisible.
- Enable lazy loading. Add loading="lazy" to below-the-fold images so they only load as the visitor scrolls. Keep above-the-fold and your LCP image eager.
Verify and maintain
Re-test in PageSpeed Insights and confirm the "properly size images" and "efficiently encode images" warnings are gone and your LCP improved. Then make compression a habit: optimize every new image before you upload it, so the problem never creeps back.
Frequently asked
What business owners ask next.
What is the best image format for websites in 2026?
WebP for photographs, with AVIF where supported for even smaller files, SVG for logos and icons, and PNG only when you need transparency. Modern formats are far smaller than legacy JPEG and PNG at the same quality.
How small should website images be?
Keep most images under 200KB, hero images under about 150KB, and total image weight on a page under 500KB. Resize to twice the display size at most and compress until just before quality loss is visible.