Web vitals monitoring
Measure Core Web Vitals:live, from your first visitor.
You don't measure website speed in a lab, you measure it on real visitors. fastmon is web vitals monitoring from Germany: LCP, INP, CLS and TTFB from every real visit, deployable GDPR-compliant and cookieless* in the default mode. Live in about five minutes.
Live on this page
This is what fastmon looks like: your visit, measured live.
No screenshot, no demo data: this page measures itself with the fastmon tracker. Below are the values of your visit to this page, measured live on your device, your network, your browser. This is exactly how you would see every visitor of your own website.
Live: this page is measuring itself
- TTFB
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- FCP
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- LCP
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- CLS
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Same browser APIs the fastmon script uses. No cookies* involved.
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Real values only: if a number is missing, your browser cannot measure that metric (Safari, for example, reports no LCP). fastmon measures exactly as honestly on your website.
The metrics
LCP, INP, CLS and TTFB, explained briefly.
The three Core Web Vitals Google ranks you by, plus TTFB as the server diagnostic. fastmon scores them at the p75 against Google's thresholds: green means 75% of your visitors were at least this fast.
How fast does the main content appear?
Largest Contentful Paint is the moment the biggest visible element (a hero image, video poster or headline) has rendered. fastmon breaks it into its four subparts, from TTFB to element render delay, so you see where the wait is.
- Good
- ≤ 2.5 s
- Needs work
- ≤ 4.0 s
- Poor
- > 4.0 s
Does the page respond instantly to taps and clicks?
Interaction to Next Paint is the worst-case delay between an interaction and the next frame. It replaced FID as a Core Web Vital in March 2024. Long Animation Frames (over 50 ms) point at the script that blocked the response.
- Good
- ≤ 200 ms
- Needs work
- ≤ 500 ms
- Poor
- > 500 ms
Does the layout jump around while loading?
Cumulative Layout Shift scores how much visible content moves unexpectedly. fastmon reports the worst shift window per visit, so a late-loading banner that pushes your content down does not hide in the average.
- Good
- ≤ 0.1
- Needs work
- ≤ 0.25
- Poor
- > 0.25
How fast does your server respond?
Time to First Byte is the time from the click to the first byte of the server response: DNS, connection, TLS and the work of your backend. Not a Core Web Vital, but a high TTFB slows everything after it, including your LCP. The first knob to turn when everything is slow.
- Good
- ≤ 0.8 s
- Needs work
- ≤ 1.8 s
- Poor
- > 1.8 s
Model calculation
What does a slow website cost you?
The Deloitte/Google study 'Milliseconds Make Millions' (2020) measured across 37 brands and over 30 million sessions how a 0.1 s faster mobile load time correlates with conversion and revenue. Run the model with your own numbers.
Your numbers
What 0.1 s costs you
€1,344/month
Model calculation, not a forecast
With your numbers, a page that is 0.1 s faster would correspond to about €1,344 more revenue per month in this model.
- Revenue today (model)
- €16,000
- Revenue with a 0.1 s faster page (model)
- €17,344
- Difference per month
- €1,344
- Difference per year
- €16,128
Model calculation based on the Deloitte/Google study 'Milliseconds Make Millions' (2020). No promise of results: your actual effect depends on your website, your industry and your implementation. fastmon measures where you lose time; the optimization is up to you.
Transparency
How we calculate
Revenue = visitors x conversion rate x order value. Model factor: +8.4% conversion per 0.1 s faster mobile load time, the retail figure from the Deloitte/Google study 'Milliseconds Make Millions' (2020). So the difference above is revenue x 0.084.
The same study also measured +9.2% average order value in retail and +10.1% conversion in travel; our model deliberately uses only the retail conversion factor. For context: per Google/SOASTA data (2017), the probability of a bounce increases 32% as load time grows from 1 s to 3 s.
Sources: Deloitte/Google 'Milliseconds Make Millions' (2020), Google/SOASTA Research (2017).
FAQ
Web vitals monitoring, answered.
The questions people ask before they measure their website speed.
What are Core Web Vitals?
Core Web Vitals are the three user-experience metrics Google measures for every website and factors into ranking: LCP (how fast the main content appears), INP (how fast the page reacts to input) and CLS (how much the layout jumps). Google scores them at the 75th percentile; good means LCP ≤ 2.5 s, INP ≤ 200 ms and CLS ≤ 0.1. fastmon measures all three from real visits, plus diagnostics like TTFB, FCP and page load time.
How do I measure my website speed?
There are two complementary ways. A lab test (Lighthouse, PageSpeed Insights) loads your page on a simulated device: reproducible, but it does not show what your visitors experience. Web vitals monitoring (Real User Monitoring) measures every real load time in your visitors' browsers, on their devices and networks, aggregated at the p75. fastmon makes this field data visible from your first visitor, without 28-day averages, and adds scheduled Lighthouse audits if you want them.
Do I need a cookie banner for web vitals monitoring?
No, not in Minimal and Standard mode. Nothing is stored on the device, and the values that get read were not there beforehand: they come into being at the moment of the page view. Naming fastmon in your privacy policy is enough. In Full mode you do need consent, because an identifier is written into sessionStorage. This classification has been reviewed with our external data protection officer; a residual risk remains, because no court has ruled on this constellation.
The full derivation, with the statutory text and the opposing readingDoes a faster website really make more revenue?
There are solid field studies on this. The Deloitte/Google study 'Milliseconds Make Millions' (2020) measured across 37 brands and over 30 million sessions that a 0.1 s faster mobile load time went along with +8.4% conversion and +9.2% average order value in retail, and +10.1% conversion in travel. Per Google/SOASTA data (2017), the probability of a bounce increases 32% as load time grows from 1 s to 3 s. These are correlations from field studies, not a guarantee for your site: your effect depends on your website, your industry and your implementation. That is why our calculator works transparently with a disclosed model factor and promises you nothing.
What does web vitals monitoring with fastmon cost?
fastmon Light starts at €29 a month with 200,000 pageviews: Core Web Vitals, Real User Monitoring, web analytics and alerts. Standard from €99 adds full debugging, synthetic monitoring and fastmon AI. Both hosted in Germany, live in about five minutes, no credit card to start.
Web vitals monitoring,
from €29 a month.
Live from your first visitor, read-only by default: no cookies*, no long-lived identifiers. Hosted in Germany.
Light
€29/month
200,000 pageviews included.
Need debugging and all features? Standard from €99 for 1M pageviews. Enterprise on request. See all plans