Best Image Format for Websites in 2025
The Performance Stakes
Images account for roughly 50-70% of the average webpage's total weight. A single unoptimized hero image can be larger than all your HTML, CSS, and JavaScript combined. Choosing the right format is the single highest-impact optimization you can make.
With Core Web Vitals now a direct ranking factor, every millisecond counts. A 500KB hero image that could be served as a 200KB WebP or 150KB AVIF directly affects your Largest Contentful Paint score.
Content Type Determines Format
The best format depends on what kind of image you are serving. Photographs with smooth gradients benefit from lossy compression formats like JPEG, WebP, or AVIF. Screenshots, UI mockups, and graphics with sharp text require lossless formats like PNG or lossless WebP.
For background textures and abstract designs, a well-compressed WebP at 40-50% quality often looks indistinguishable from the original. For product photos on an e-commerce site, you may want to use JPEG at 85% quality to avoid any visible artifacts that might reduce perceived product quality.
Next-Gen Format Strategy
The recommended strategy is to use the picture element with multiple source formats. This lets you serve AVIF to browsers that support it, fall back to WebP for most modern browsers, and finally default to JPEG or PNG for legacy browsers like Internet Explorer.
- AVIF: Best compression (50%+ smaller than JPEG), but narrowest browser support
- WebP: Great compression (25-35% smaller than JPEG), excellent browser coverage
- JPEG: Universal fallback. Use at 80-85% quality as baseline
- PNG: Only for graphics requiring transparency or lossless precision
Core Web Vitals Impact
Largest Contentful Paint (LCP) is directly affected by image loading performance. Google recommends using next-gen formats as one of the primary optimizations for improving LCP scores.
Beyond format, consider implementing lazy loading, responsive image srcsets, and preloading hero images. The combination of the right format with proper loading techniques can cut LCP times by 40-60%.
Implementation Guide
Start by auditing your current images. Identify which pages have the largest image payloads and prioritize converting those images to WebP or AVIF. Use automated tools in your build pipeline to generate multiple format variants.
Always serve images at the exact display size specified in your CSS. Uploading a 4000px-wide photo and resizing it with CSS wastes bandwidth on data that gets discarded. Use our Image Resizer to create appropriately sized variants for different breakpoints.
Frequently Asked Questions
Should I convert all my existing JPEGs to WebP?
Yes, if you want better performance. Converting your existing JPEG library to WebP can save 25-35% bandwidth without visual quality loss. Prioritize hero images, product photos, and background images that appear above the fold.
How do I serve different image formats to different browsers?
Use the HTML picture element with source tags for each format. List formats in order of preference (AVIF first, then WebP, then JPEG/PNG fallback). Modern browsers will pick the first format they support.
Is AVIF production-ready for websites?
AVIF is production-ready for audiences using modern browsers (Chrome, Firefox, Safari 16.4+). For general audiences, use AVIF with a WebP fallback to ensure full coverage. The encoding is slower than WebP, so generate AVIF during build rather than on-the-fly.
Does using next-gen formats actually improve SEO?
Indirectly, yes. Next-gen formats reduce file sizes, which improves page load speed and Core Web Vitals scores. Google has confirmed that page speed and Core Web Vitals are ranking factors, so faster-loading images can improve your search rankings.