Image Optimization Checker
Checks images declare width/height and use lazy-loading below the fold.
What this tool checks
Images declare width and height
Checks <img> elements set explicit width and height (or an aspect-ratio via CSS).
Why it matters: Images without intrinsic dimensions cause layout shift (CLS) as they load, hurting the user experience and Core Web Vitals.
If it fails: Add width and height attributes to <img> elements so the browser can reserve space.
Source: web.dev/articles/optimize-cls
Below-the-fold images use lazy loading
Reports how many images use loading="lazy".
Why it matters: Lazy-loading offscreen images reduces initial page weight and speeds up the first render. The first (LCP) image should NOT be lazy-loaded.
If it fails: Add loading="lazy" to images that are likely below the fold; keep the main hero image eagerly loaded.
Related tools
- Deprecated HTML Tags CheckerScans for obsolete HTML elements like <center>, <font> and <marquee>.
- GZIP Compression TestChecks the HTML response is served with gzip, brotli or deflate compression.
- Inline CSS CheckerCounts elements using a style="" attribute instead of a stylesheet.
- Google AMP TesterReports whether the page is itself an AMP page or declares an amphtml alternate.
- Webpage File Size CheckerTotal download size of the rendered page, broken down by resource type.
- Webpage JavaScript Error CheckerLoads the page in a real browser and reports any JavaScript errors thrown.