Dev.to
7/8/2026
Image Optimization for Core Web Vitals: A Practical Guide to WebP, AVIF, and Bulk Conversion
Original: Why Your Images Are Killing Your Core Web Vitals (and How I Fixed It in One Afternoon)
Short summary
Images typically account for 60–70% of page weight and dominate Largest Contentful Paint scores, making them the highest-ROI target for Core Web Vitals optimization. WebP delivers 60–80% smaller files than JPEG at equivalent quality with 97%+ browser support, while AVIF squeezes an additional 20–30% at the cost of slower encoding. The author introduces BatchSet, a browser-based bulk image converter that handles batch format conversion, AI background removal, and URL-based ingestion from e-commerce catalogs.
- •Images are the top culprit in poor Core Web Vitals, often 60–70% of page weight
- •WebP reduces file size 60–80% vs JPEG; AVIF adds another 20–30% but encodes slower
- •BatchSet tool offers free bulk conversion with AI background removal and spreadsheet/URL batch mode
Generated with AI, which can make mistakes.
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