LCP
Largest Contentful Paint
Time until the largest element in the viewport is rendered. It is often a hero image or a large heading.
Good≤ 2.5 s Warn2.5–4 s Poor> 4 s
Free quick site scan
Paste a public URL to check early performance and configuration signals. Result scope depends on the available data source.
No account No card Public URL
Check a page without creating an account
Audit duration depends on the mode, page response and measurement-service availability. You receive Lighthouse results or a report from fetching the public page.
Enter to start
/ About the tool
What is a website performance audit?
The public Auditor uses CometWeb’s PageSpeed Insights key when configured — you do not need your own key. Without it, you still get HTTP checks on a public URL.
Result scope depends on the data source. The report states whether it contains Lighthouse data, HTTP analysis, or both sources.
Recommendations describe detected signals and estimated savings where the source provides them. Review each recommendation before implementation.
/ Metric glossary
Five metrics describing website performance.
Each metric describes a different aspect of loading or interface response. Metric availability depends on measurement mode.
INP
Interaction to Next Paint
Delay between a user interaction and the next interface update. INP replaced FID as a Core Web Vital in March 2024.
Good≤ 200 ms Warn200–500 ms Poor> 500 ms
CLS
Cumulative Layout Shift
The total of unexpected layout shifts while the page loads. A high CLS means visible elements change position.
Good≤ 0.1 Warn0.1–0.25 Poor> 0.25
TTFB
Time to First Byte
Time from sending an HTTP request to receiving the first response byte, including backend, DNS, TLS and routing delay.
Good≤ 200 ms Warn200–500 ms Poor> 500 ms
FCP
First Contentful Paint
The point when the browser renders the first content element, such as text, an image or an SVG.
Good≤ 1.8 s Warn1.8–3 s Poor> 3 s
/ When to use it
Four moments when you should repeat an audit.
After a release
Check selected pages and compare publicly detectable signals with the previous result.
Before a campaign
Review technical risks on key pages before increasing traffic.
After a refactor
Compare results before and after the change to identify possible regressions.
Public-signal comparison
Check publicly available indicators for selected pages using the same scope.
/ FAQ
Frequently asked questions
Can’t find an answer? Contact us — we reply on business days, 09:00–17:00 CET.
/ Comparison
CometWeb Auditor and alternatives
Each tool has a different measurement scope and configuration. This comparison is not about a fixed run time.
History and alerts depend on the product and plan. The free Auditor has neither — see CometWeb Insight — for working with results, priorities and follow-up verification.
This tool patches one problem at a time
The Performance module in Insight does the same in every audit: Core Web Vitals in every audit — with priorities, history and before/after comparison.