—ms
Time until initial HTML parsing completes.
← Back to BenchLab BENCHLAB / WEB TOOLS DOM CONTENT LOADED PAGE LOAD TIME TO FIRST BYTE TRANSFERRED RESOURCES
LCP Checking… CLS Checking… INP Not measured
Page Performance
Measure page loading, browser responsiveness, and resource usage using performance data exposed by your browser.
TEST TARGET
This page
Analyze the page you are currently viewing. Some metrics are only available during the original page load.
—ms
Time until the page load event completes.
—ms
Navigation start until the first response byte.
—
Resources visible to the browser's Resource Timing API.
NAVIGATION TIMELINE
Reading browser data… Where time is spent
Collecting navigation timings…
Navigation timing is measured relative to the browser's navigation start. It describes this page's load, not the performance of every website.
RESOURCE ANALYSIS
— resources Resource breakdown
| Resource type | Count | Transfer size | Decoded size |
|---|---|---|---|
| Reading resource data… | |||
Cross-origin resources may hide timing details unless the remote server permits timing access. A zero transfer size can also indicate cached data or unavailable size information.
RUNTIME RESPONSIVENESS
Interaction check
Run a short JavaScript workload to estimate how long this browser takes to complete a repeatable block of main-thread work.
—ms
Ready to test.
This is a synthetic JavaScript test, not Interaction to Next Paint (INP) or a Core Web Vital. Results depend on the CPU, browser, and current system load.
CORE WEB VITALS
Metric availability
Largest Contentful Paint
Cumulative Layout Shift
Interaction to Next Paint
LCP and CLS can be observed during this visit, but they may not represent a fresh navigation. INP requires real user interaction observations over time; this page does not claim to calculate a valid INP score.
ABOUT THIS TOOL
How to read the results
Page Performance combines browser navigation timing, resource timing, a synthetic JavaScript check, and supported LCP/CLS observations for this page. It is not a complete Core Web Vitals assessment and does not measure INP.
Navigation timing
- DOMContentLoaded
domContentLoadedEventEnd: navigation start to completion of the DOMContentLoaded event.- Page load
loadEventEnd: navigation start to completion of the load event.- Response start
responseStart: a TTFB-style navigation-start-to-first-response-byte value, not server processing time alone.
The timeline also shows redirect, DNS lookup, connection, request wait, response download, DOM processing, and load-event stages. Each is derived by subtracting the corresponding Navigation Timing timestamps and clamped to zero for display.
Resources and JavaScript
Resource count is the number of entries returned by
performance.getEntriesByType("resource"). Entries are
grouped by initiatorType; each group sums the browser's
reported bytes transferred (transferSize) and decoded
resource-body bytes (decodedBodySize). Sizes are
formatted with binary 1024-based B/KB/MB/GB units.
The responsiveness check yields for 50 ms, then runs a synchronous
1.2-million-iteration square-root/sine loop three times. Each run
uses performance.now(); the displayed value is the
middle sample after numeric sorting. There is no warm-up or score.
LCP, CLS, and limitations
When supported, LCP is observed with a buffered
PerformanceObserver and displays the latest observed
entry's startTime. CLS observes buffered layout-shift
entries, ignores entries with recent input, accumulates shifts when
they are within a 1-second gap and 5-second session window, and
reports the largest session value observed.
API support varies. Cross-origin resources may hide timing details; cached resources can report zero transfer size, and browser policies can limit which entries are exposed. Results describe this current page and its network, device, browser, and system workload—not every page or a complete real-user experience. Compare the same page under similar cache and workload conditions, close unnecessary activity, and repeat tests when practical.