Diagnose loading and layout shifts
LCP helps identify the main element that appears late; CLS describes layout instability. Use the separate INP test to investigate delays after a click.
LCP: 1.9sCLS: 0.04TBT: 120msLab example
Website speed test online
Enter a URL to find what slows the page down: images, scripts or the server response. Use the report to trace loading delays and layout shifts, then choose what to fix first.
Advanced settings
What the report includes
A website speed report with priorities for engineering
Every recommendation is tied to a metric, resource, and technical cause, so the team can see what to fix first and what can stay in the backlog.
Resource and request map
The HTTP waterfall shows what blocks rendering, which resources use parallel connections, and where third-party scripts slow down the start.
index.html142ms
main.css380ms
app.js1.2s
hero.webp720ms
inter.woff2210ms
Prioritized optimization plan
Milten groups issues into a short task list for LCP, CLS, TBT, TTFB, third-party scripts, and heavy resources.
01LCP: compress and preload hero mediaP1
02CLS: lock card dimensionsP2
03TTFB: check HTML cachingP3
How it works
How Milten checks website speed
Test website speed under the selected conditions. Get lab loading metrics and findings; one test does not replace measurements from real visitors.
01 · URL
Enter a URL for the speed check
Check a homepage, landing page, catalog, or product page. Milten opens the page in a browser and applies the selected region, network, and device.
02 · SCAN
Measure loading and visual stability
Collect lab metrics, network delays, heavy resources and layout shifts. TTFB measures server response delay; TBT measures main-thread blocking during loading.
03 · PLAN
Decide what to fix first
Start with a finding and its evidence: which resource delayed loading or which element shifted the layout. Fix the cause and rerun with the same settings.
What we measure
Website speed metrics: FCP, LCP, CLS, TBT, TTFB, and SI
The scanner separates perceived loading, layout stability, JavaScript blocking, and server response speed so optimization is not reduced to a single score.
FCP
First Contentful Paint
When the user first sees text, an image, or SVG: an early signal that the page has truly started loading.
Good<= 1.8s
Needs<= 3s
Poor> 3s
LCP
Largest Contentful Paint
Time until the main visible element renders: a hero image, large heading, product card, or catalog block.
Good<= 2.5s
Needs<= 4s
Poor> 4s
CLS
Cumulative Layout Shift
The sum of unexpected layout shifts: banners, unsized images, late fonts, and blocks that move content after loading.
Good<= 0.1
Needs<= 0.25
Poor> 0.25
TBT
Total Blocking Time
How long the main thread was busy with long JavaScript tasks and could not respond quickly to user actions.
Good<= 200
Needs<= 600
Poor> 600
TTFB
Time to First Byte
Delay before the first byte of HTML: backend, DNS, TLS, CDN, and cache time before the browser starts receiving the page.
Good<= 0.8s
Needs<= 1.8s
Poor> 1.8s
SI
Speed Index
How quickly the visible viewport fills in: this helps explain why a page feels slow even when individual metrics look good.
Good<= 3.4s
Needs<= 5.8s
Poor> 5.8s
FAQ
Frequently asked questions about website speed checks
Short answers about Core Web Vitals, SEO, and practical page optimization.
What are Core Web Vitals and how do they affect SEO?
Core Web Vitals cover loading (LCP), responsiveness (INP) and visual stability (CLS). Field data is needed to assess the experience of real visitors. Speed Scanner helps diagnose causes in a lab run; TBT is not a substitute for INP. Good values do not guarantee higher rankings.
How do I check my website speed?
Enter the URL in the form above, choose a mobile or desktop profile, and click “Check website”. The scanner measures loading performance, collects HAR, shows FCP, LCP, CLS, TBT, TTFB, Speed Index, and creates a technical task list.
What should I do if LCP is too high?
First find the LCP element: it may be a hero image, large heading, banner, or product card. Then check preload, critical CSS, media weight, CDN, caching, and render-blocking resources that delay rendering.
How long does a website analysis take?
A quick check usually takes under a minute, but exact time depends on the selected region, network profile, CPU throttling, and the number of resources on the page. For stable conclusions, compare several runs under the same conditions.
How do I fix CLS issues?
Set width, height, or aspect-ratio for media, reserve space for banners and widgets, avoid inserting new content above the visible area, and configure fonts with font-display and preload. In the report, look not only at the final CLS, but also at the elements that contributed the most.
Related services
Tools for deeper performance optimization
Page responsiveness (INP)
Measure how quickly the page responds to automated actions. Find delays during the test run.
OpenBack / Forward cache
Check whether the browser uses its cache when navigating back and forward. Find out what prevents caching.
OpenMemory leaks
Find data that stays in memory after repeated navigation. Review possible leaks and accumulating data.
OpenJavaScript check
Check JavaScript files, loading errors, and code unused during loading. Find scripts that need further investigation.
Open