Why image size directly affects search rankings
Google measures page load speed through Core Web Vitals — specifically Largest Contentful Paint (LCP), which tracks how long it takes for the main visible element to load. For most pages, the LCP element is an image. A 4 MB hero photo on a slow connection can push LCP above 4 seconds, which Google classifies as “Poor” and factors into search rankings.
The target: LCP under 2.5 seconds. For most web hosts, that means keeping hero images under 400 KB and content images under 200 KB. A modern phone photo at 4–8 MB needs 95%+ size reduction to hit those targets — but quality at 85% JPEG compression is visually identical on screen at normal zoom.
Recommended sizes by image type
Hero images (full width): 1920 px wide, under 400 KB. Use the resize tool after converting to set the exact pixel width.
Content images (in-article): 800–1200 px wide, under 200 KB. These load within text columns and don't need the full viewport width.
Thumbnails and card images: 400–600 px wide, under 100 KB. Small enough that JPEG quality 85 still looks sharp at the display size.
Background images: Match your CSS container width exactly. A 1920 px background image on a 1400 px max-width site wastes bandwidth and gains nothing visually.
Compressing without a third-party server
For agency work and client projects, compressing client photos through an external service means those photos pass through someone else's infrastructure. LocalJPG compresses entirely in your browser — the image never leaves your device. This is relevant for client portrait photos, product shots under NDA, or any image with commercial sensitivity.
Related: Compress to 200 KB · Compress to 500 KB · TinyPNG alternative · Shopify product images