速度
レスポンシブ画像
重要な理由
Without srcset or <picture>, phones download the same large image files as desktop screens. That wastes mobile data and slows Largest Contentful Paint.
修正方法
- Generate several sizes of each image and list them in srcset with a sizes attribute.
- Most CMSs (WordPress, Shopify) do this automatically if images are inserted through the media library.
次のツールで確認
- Image Alt Text Checker – Find images with missing alt text, missing dimensions and no lazy loading.
- Page Size Checker – Find the total weight of a page and which images, scripts and styles are heaviest.
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