{"id":354,"slug":"webp-25-34-smaller-than-jpeg-google-study","title":"Google WebP Compression Study: WebP is 25-34% smaller than JPEG at equivalent SSIM (avg ~30%)","kind":"reference","scope":"business","status":"current","audiences":["claude-code","dev","candid-team"],"topics":["core-web-vitals"],"reference_body":"**Claim:** Per Google's WebP Compression Study (updated August 7, 2025), **WebP is 25-34% smaller than JPEG** at equivalent SSIM index. Google's own FAQ summarises this as *\"an average of 30% more compression than JPEG.\"*\n\n**Source:** <https://developers.google.com/speed/webp/docs/webp_study>\n\n**Confidence:** Verified (Google primary).\n\n**Practical implication:** Modern image formats (WebP, AVIF) are the lowest-effort, highest-yield CWV improvement available. AVIF is even better than WebP for some image classes (20-50% smaller than JPEG depending on content). Use `<picture>` with AVIF + WebP + JPEG fallback for broad browser support.","rationale_body":null,"metadata":null,"links":{"outgoing":[],"incoming":[{"slug":"lcp-killers-catalogue","title":"Reference: the 8 most common LCP killers — ranked by observed frequency","kind":"reference","scope":"business","link_type":"depends-on"},{"slug":"rule-preload-hero-image-with-fetchpriority","title":"RULE: The LCP image always has explicit width/height + fetchpriority=\"high\" + no lazy-loading","kind":"rule","scope":"business","link_type":"depends-on"},{"slug":"research-brief-page-speed-moat","title":"Research brief: Page Speed as a Moat — why CWV separates the agencies from the freelancers (piece 9 of 15)","kind":"reference","scope":"business","link_type":"relates-to"}]},"created_at":"2026-05-22T20:03:33.392Z","updated_at":"2026-05-22T20:03:33.392Z"}