Boosting Initial Page Speeds with Lazy-Loaded Frames and Images

Sun, 20 Jul 2025 00:00:00 +0900

Introduction

An effective but frequently overlooked strategy for optimizing web page speeds is deferring off-screen asset loading.

By default, when a user loads a web page, the browser immediately requests all images and <iframe> elements (like YouTube embeds, interactive maps, social widgets, or advertising scripts) on the page, even if they are located far below the fold. This concurrent downloading blocks the main thread and slows down your page’s First Contentful Paint (FCP) time.

Iframe on Commentary of Takao

Boosting Initial Page Speeds with Lazy-Loaded Frames and Images

Introduction