How to Resize Images for Website – Speed & SEO Guide

Page speed is a confirmed Google ranking factor. Images are the largest elements on most web pages — and the most commonly oversized. Learning how to resize images for website use is one of the most impactful optimizations you can make for both user experience and SEO.

Why website image sizes matter for SEO

Google's Core Web Vitals measure three key aspects of page experience. Largest Contentful Paint (LCP) directly measures how fast the biggest visible element — usually a hero image or banner — loads. If that image is 3 MB because it was uploaded straight from a camera, your LCP score will be poor regardless of how fast your server is.

Slow pages increase bounce rates. High bounce rates signal to Google that users aren't finding what they need — which can lower your rankings over time.

Recommended image dimensions for websites

• Hero/banner images: 1920 × 1080 px, under 200 KB as WebP
• Blog post featured images: 1200 × 628 px or 1200 × 800 px, under 150 KB
• Product images (e-commerce): 800 × 800 px, under 80 KB as WebP
• Thumbnail images: 400 × 300 px, under 40 KB
• Author avatars: 96 × 96 px or 150 × 150 px
• Logo: 200–400 px wide (PNG with transparency or SVG)

Step-by-step: resize images for website with Resizo

• Step 1: Identify the maximum display width of the image on your website. Check in your CMS or inspect the element in your browser's developer tools.
• Step 2: Open Resizo and drop your image.
• Step 3: Set the width to match your display dimension (e.g., 1200px for a blog featured image).
• Step 4: Select WebP as output format for the smallest file size.
• Step 5: Download and upload to your CMS. Your image is now correctly sized for web.

The 2× rule for retina displays

Retina and high-DPI displays render images at 2× density, meaning a 600px container actually needs a 1200px image to appear sharp. For hero images and important visuals, upload at 2× the display size. For thumbnails and secondary images, 1× is usually sufficient.

Use WebP for maximum performance

WebP is the recommended format for web images in 2026. It delivers 25–35% smaller files than equivalent JPG/PNG while maintaining comparable visual quality. All major browsers have supported WebP since 2020.

When you resize images for website using Resizo, switch the output format to WebP as a default. The resulting files will load faster, improving your LCP scores and overall page speed.