Image Performance Checker
Check image number, known image size, lazy loading, and missing dimensions as risks to LCP, CLS, and mobile loading time.
Technical pre-testing without browser rendering. Own scores of 0–100 mean: higher = less recognized risk signals. No measured LCP, INP or CLS values. TTFB is measured on the server side.
Ideal for shops, magazines, landing pages, portfolio pages and CMS templates with many pictures.
Results
Technical pre-checking of a URL. For a crawl over many URLs, use the premium audit.
Findings
Detailed hit
Practical example · for illustration
Deliver an oversized product image appropriately
Example: For a 400-pixel tile, a 3,000-pixel image is loaded. Create suitable sizes and deliver a suitable variant for the layout with srcset and sizes. Check lazy loading for images outside of the first range of view.
What does not prove the result
The browser selects image variants depending on the viewport and pixel density. The HTML retrieval does not fully replicate this selection; control the actual loaded file in the network panel.
Deepen with PageSpeed Insights and available field data · Google's Definition of Core Web Vitals
What the Image Performance Checker evaluated
The pre-check evaluates the retrieved HTML and a limited sample of linked resources. It does not execute JavaScript and does not simulate user interactions. Findings are concrete occasions for an examination in the browser; an inconspicuous result does not exclude performance problems.
From a single check to Core Web Vitals Audit
The audit examines multiple URLs and helps to find recurring technical patterns in templates. This way you can see if a change affects several pages and where you can start the implementation.
Questions about Image Performance Checker
Which image formats make sense?
WebP and AVIF are often significantly smaller than JPEG or PNG. But also decisive are dimensions, compression and responsive variants.
Should every image be loaded lazy?
No. The Hero or LCP image should usually be loaded early and prioritized; downstream images are suitable for lazy loading.
Why are there standalone tools in addition to the audit?
Individual tools help with a specific URL or technical problem. The audit compares these signals across multiple URLs and shows recurring patterns.
Is the individual check free of charge?
Yes. The standalone tools check a single URL. For larger crawls, complete tables and CSV export, the premium audit is planned.