Understanding Your Metrics

Real User Monitoring collects a comprehensive set of performance metrics from your actual visitors. This guide explains each metric, what it means, and how to improve it.

Core Web Vitals

These are Google's official metrics for measuring user experience and are used as ranking factors for search results.

Largest Contentful Paint (LCP)

What it measures: The time when the largest visible content element (image, video, or text block) becomes visible in the viewport.

Why it matters: LCP represents perceived loading speed. Users consider a page "loaded" when the main content is visible.

Thresholds:

  • 🟢 Good: ≤ 2.5 seconds

  • 🟡 Needs Improvement: 2.5 - 4.0 seconds

  • 🔴 Poor: > 4.0 seconds

Common causes of poor LCP:

  • Large, unoptimized images

  • Slow server response times

  • Render-blocking JavaScript and CSS

  • Slow resource load times

How to improve:

  • Optimize and compress images

  • Use smoxy's image optimization features

  • Enable browser caching

  • Use a CDN (smoxy does this automatically)

  • Implement lazy loading for below-the-fold images

  • Minimize server response time (TTFB)

Interaction to Next Paint (INP)

What it measures: The responsiveness of a page to user interactions - how quickly the page responds to clicks, taps, and keyboard inputs.

Why it matters: INP measures how quickly users can interact with your page. High INP means users experience delays when clicking buttons or links, leading to frustration.

Thresholds:

  • 🟢 Good: ≤ 200 milliseconds

  • 🟡 Needs Improvement: 200 - 500 milliseconds

  • 🔴 Poor: > 500 milliseconds

Common causes of poor INP:

  • Heavy JavaScript execution blocking the main thread

  • Large JavaScript bundles

  • Long-running event handlers

  • Unoptimized third-party scripts

How to improve:

  • Break up long JavaScript tasks

  • Use web workers for heavy computations

  • Minimize third-party scripts

  • Optimize event handlers

  • Enable JavaScript minification in smoxy

  • Use code splitting to reduce bundle sizes

Cumulative Layout Shift (CLS)

What it measures: Visual stability - how much content shifts around unexpectedly while the page loads.

Why it matters: Unexpected layout shifts cause users to accidentally click wrong elements or lose their reading position, creating a frustrating experience.

Thresholds:

  • 🟢 Good: ≤ 0.1

  • 🟡 Needs Improvement: 0.1 - 0.25

  • 🔴 Poor: > 0.25

Common causes of poor CLS:

  • Images without dimensions (width/height attributes)

  • Ads, embeds, or iframes without reserved space

  • Web fonts causing text to reflow (FOIT/FOUT)

  • Dynamically injected content

  • Animations that trigger layout changes

How to improve:

  • Always include width and height attributes on images and videos

  • Reserve space for ads and embeds with CSS

  • Use font-display: optional or font-display: swap for web fonts

  • Avoid inserting content above existing content

  • Use CSS transforms for animations instead of properties that trigger layout

Page Timing Metrics

Time to First Byte (TTFB)

What it measures: The time from the browser making a request to receiving the first byte of the response from the server.

Why it matters: TTFB represents server processing time and network latency. It's the foundation for all other performance metrics.

Thresholds:

  • 🟢 Good: < 200 milliseconds

  • 🟡 Acceptable: 200 - 500 milliseconds

  • 🔴 Poor: > 500 milliseconds

How to improve:

  • Optimize server-side code and database queries

  • Use server-side caching

  • Enable HTTP/2 or HTTP/3

  • Use a CDN (smoxy provides this)

  • Optimize origin server performance

  • Reduce server-side processing time

First Contentful Paint (FCP)

What it measures: The time when the first piece of content (text, image, SVG, or canvas) is rendered on the screen.

Why it matters: FCP provides feedback to users that the page is loading, reducing perceived load time.

Thresholds:

  • 🟢 Good: < 1.8 seconds

  • 🟡 Needs Improvement: 1.8 - 3.0 seconds

  • 🔴 Poor: > 3.0 seconds

How to improve:

  • Reduce render-blocking resources

  • Inline critical CSS

  • Preload key resources

  • Minimize server response time

  • Enable text compression (smoxy does this automatically)

Total Blocking Time (TBT)

What it measures: The total time during page load when the main thread was blocked long enough to prevent input responsiveness.

Why it matters: High TBT means the page appears loaded but is unresponsive to user input.

Thresholds:

  • 🟢 Good: < 200 milliseconds

  • 🟡 Needs Improvement: 200 - 600 milliseconds

  • 🔴 Poor: > 600 milliseconds

How to improve:

  • Reduce JavaScript execution time

  • Split long tasks into smaller ones

  • Remove unused JavaScript

  • Minimize third-party code

  • Use code splitting and lazy loading

Resource Timing Metrics

Page Load Time

What it measures: The total time from navigation start to the page fully loading (including all resources).

Why it matters: Overall page performance indicator.

Target: < 3 seconds for good user experience

Server Response Time

What it measures: Time spent waiting for the server to generate and send the initial HTML response.

Why it matters: Slow server processing delays everything else.

How to improve:

  • Optimize database queries

  • Use server-side caching

  • Upgrade server resources if needed

  • Implement application performance monitoring

Content Transfer Time

What it measures: Time spent downloading the initial HTML document.

Why it matters: Large HTML files slow down initial rendering.

How to improve:

  • Minimize HTML size

  • Enable gzip/brotli compression (smoxy does this)

  • Reduce inline scripts and styles

Total Byte Weight

What it measures: Total size of all resources loaded on the page (HTML, CSS, JavaScript, images, fonts, etc.).

Why it matters: Larger pages take longer to download, especially on slower connections. Each megabyte matters for mobile users.

Thresholds:

  • 🟢 Good: < 1 MB

  • 🟡 Acceptable: 1-3 MB

  • 🔴 Heavy: > 3 MB

How to improve:

  • Optimize and compress images with smoxy's image optimization

  • Minify CSS and JavaScript (enable in smoxy settings)

  • Remove unused code

  • Use modern image formats (WebP, AVIF) (smoxy auto converts images)

  • Implement lazy loading

  • Use responsive images with srcset

Network Timing Metrics

DNS Lookup Time

What it measures: Time to resolve the domain name to an IP address.

Why it matters: DNS lookups add latency before connection can begin.

Typical values:

  • Cached: 0ms

  • First visit: 20-120ms

How to improve:

  • Use a fast DNS provider

  • Implement DNS prefetching for external domains: <link rel="dns-prefetch" href="//example.com">

  • Reduce number of different domains your page loads resources from

Initial Connection Time

What it measures: Time to establish a TCP connection to the server.

Why it matters: Each new connection adds latency.

Typical values: 20-200ms depending on geographic distance

How to improve:

  • Enable HTTP/2 or HTTP/3 for connection reuse

  • Use a CDN to reduce geographic distance (smoxy provides this)

  • Minimize the number of domains

  • Implement connection prewarming: <link rel="preconnect" href="//example.com">

SSL Time

What it measures: Time to complete the SSL/TLS handshake.

Why it matters: HTTPS adds overhead, but is necessary for security and HTTP/2.

Typical values: 50-200ms

How to improve:

  • Enable TLS 1.3 (faster handshake)

  • Use OCSP stapling

  • Implement TLS session resumption

  • Use modern cipher suites

Device & Context Data

Device Type

Your data is automatically segmented by:

  • Desktop: Traditional computers

  • Mobile: Smartphones

  • Tablet: Tablet devices

Why it matters: Different devices have vastly different performance characteristics. Mobile devices typically have slower CPUs and network connections.

Best practice: Always check performance across all device types, as mobile often performs significantly worse.

Geographic Data

Country, City, Location

RUM tracks where your users are located.

Why it matters:

  • Users farther from your servers experience higher latency

  • Regional performance issues can be identified

  • CDN effectiveness can be measured

How to use this data:

  • Identify regions with poor performance

  • Optimize CDN configuration

  • Consider regional server placement for key markets

  • Understand your audience distribution

Network Data

ISP & ASN (Autonomous System Number)

Information about the user's Internet Service Provider.

Why it matters: Some ISPs have consistently better or worse performance to your servers.

How to use this data:

  • Identify ISPs with poor connectivity

  • Troubleshoot regional network issues

  • Optimize routing for major ISPs

Interpreting Your Data

The 75th Percentile

smoxy RUM uses the 75th percentile (p75) for Core Web Vitals, following Google's recommendations.

What this means: 75% of your users experience this value or better. This provides a balanced view that isn't skewed by outliers while still accounting for users with slower experiences.

Example: If your LCP p75 is 2.0 seconds:

  • 75% of users see LCP of 2.0s or faster

  • 25% of users see LCP slower than 2.0s

Good vs. Poor Classification

Each metric has thresholds that classify performance:

  • Good: Meeting recommended targets

  • Needs Improvement: Close to targets but could be better

  • Poor: Failing to meet minimum standards

Focus on moving "Poor" metrics to "Needs Improvement" first - these have the biggest impact on user experience and SEO.

What to Optimize First?

Priority Order

  1. Core Web Vitals (LCP, INP, CLS)

    • Direct SEO impact

    • Strong correlation with user satisfaction

  2. TTFB & Server Response Time

    • Foundation for all other metrics

    • Often easiest to improve with caching

  3. Total Byte Weight

    • Major impact on mobile users

    • Improves multiple metrics

  4. Blocking Time & INP

    • Critical for interactivity

    • Affects user engagement

Quick Wins

Start with these high-impact, low-effort optimizations:

✅ Enable image optimization in smoxy ✅ Enable HTML/CSS/JS minification in smoxy ✅ Add width and height to all images ✅ Enable browser caching ✅ Compress large images before upload ✅ Remove unused third-party scripts

Next Steps

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