Performance Fundamentals
LCP Explained: What It Is, Why It Matters, and How to Fix It
A plain-English guide to Largest Contentful Paint — what causes a slow LCP, and the five changes that make the biggest difference.
Read Article →
Chrome Extension • Free • Real-Time Performance
Know Your Site's Speed
As You Browse It
Vital Lens sits in your browser and captures Core Web Vitals — LCP, CLS, INP, FCP, and TTFB — the moment a page loads. No reports to schedule. No dashboards to open. Just instant clarity.
5+
Vitals Tracked
0
Setup Required
<1s
Capture Time
100%
Free to Use
See It In Action
Performance at a Glance,
Right in Your Browser
Open Vital Lens on any page — or pin it as a sidebar — and get a full Core Web Vitals snapshot instantly. No sign-in. No setup. No waiting.
Popup View
Sidebar View
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VitalLens
yoursite.com/
Overview
History
Compare
Resources
Settings
100
SCORE
Good
All Core Web Vitals are healthy
Captured just now
LCP
324ms
Good
CLS
0.000
Good
INP
40ms
Good
FCP
304ms
TTFB
35ms
🔍 Inspect LCP
📌 Pin Baseline
⚡ PageSpeed
Live Core Web Vitals
LCP, CLS, and INP are captured automatically as each page loads — no manual refresh needed. Watch your score update in real time as you navigate.
LCP Element Inspector
Click "Inspect LCP" to see the exact DOM element responsible for your largest contentful paint — with its CSS selector and source type so you know precisely what to optimize.
Resource Breakdown
See every resource loaded by the page — CSS, JS, images, fonts, and fetch calls — with file sizes and load times. Spot what's slowing things down in seconds.
Performance Budget Alerts
Set custom thresholds for each metric. When a page breaks your budget, Vital Lens notifies you immediately — in the extension or as a browser notification.
Full Feature Set
Five Tabs. Complete Performance Picture.
Every tab in Vital Lens is built around a specific performance question — together they give you everything you need to diagnose and improve page speed.
01
Overview
The moment a page loads, Vital Lens captures LCP, CLS, INP, FCP, and TTFB and rolls them into a single score out of 100. See at a glance whether the page is Good, Needs Improvement, or Poor — and jump into LCP element inspection or PageSpeed directly from the panel.
02
History
Every measurement is automatically stored. The History tab shows recent captures for the current domain — including LCP, CLS, and INP values alongside timestamps. Track regressions over time without a single extra click, and retain data for up to 30 days.
03
Compare
Pin a baseline snapshot of any page, then compare future measurements against it. See exactly how a code change, a new plugin, or a third-party script affected your vitals — before and after, side by side.
04
Resources
A full inventory of every resource loaded by the page — stylesheets, scripts, images, fonts, and fetch calls — with file sizes and individual load times. Filter by type to isolate heavy assets and know exactly what's adding weight to your page.
05
Settings
Define your own performance budgets for LCP, CLS, INP, and FCP. Toggle browser notifications to get alerted the moment a page breaches your thresholds. Configure data retention and clear history per domain when needed.
06
Suggest a Feature
Have an idea that would make Vital Lens even more useful for your workflow? We build what our users actually need. Send us a note and help shape what comes next.
The Metrics That Matter
What Vital Lens Tracks — and Why It Matters
Google uses Core Web Vitals as ranking signals. Each metric measures a different dimension of how users experience your page. Vital Lens keeps all of them visible as you browse.
LCP
Largest Contentful Paint
Measures how long it takes for the largest visible element — a hero image, heading, or block of text — to render on screen. It's the most direct proxy for "how fast does this page feel?"
Good: < 2.5s
Needs work: 2.5–4s
Poor: > 4s
CLS
Cumulative Layout Shift
Measures how much the page layout shifts unexpectedly during load. A high CLS score means users are clicking the wrong things as content jumps around.
Good: < 0.1
Needs work: 0.1–0.25
Poor: > 0.25
INP
Interaction to Next Paint
Measures the responsiveness of the page to user interactions — clicks, taps, and keyboard input. A slow INP makes your page feel sluggish even after it loads.
Good: < 200ms
Needs work: 200–500ms
Poor: > 500ms
FCP
First Contentful Paint
Measures the time from navigation to when any content is first rendered on screen. A fast FCP reassures users that the page is actually loading.
Good: < 1.8s
Needs work: 1.8–3s
Poor: > 3s
TTFB
Time to First Byte
Measures the time between the browser requesting a page and receiving the first byte from the server. A slow TTFB is typically a hosting, caching, or server-side problem.
Good: < 800ms
Needs work: 800ms–1.8s
Poor: > 1.8s
Simple Setup
Up and Running in Under a Minute
No account. No configuration. No API keys. Install once and Vital Lens works silently in the background on every page you visit.
1
Install from Chrome Web Store
One click to add Vital Lens to Chrome. No login or permissions beyond the current tab needed.
2
Navigate to Any Page
Browse your site, a client's site, or a competitor's page. Vital Lens captures vitals automatically on every navigation.
3
Open as Popup or Sidebar
Click the extension icon for a quick popup view, or pin it as a persistent sidebar to keep metrics visible as you browse.
4
Inspect, Compare & Act
Drill into the LCP element, check the resource list, compare against your baseline, or open PageSpeed for deeper analysis.
Who It's Built For
Made for Everyone Who Cares
About How Fast Their Site Feels
Whether you're shipping a new feature, optimizing a product page, or auditing a client's site — Vital Lens fits right into your workflow.
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Shopify Store Founders
Page speed directly affects conversion rates. A slow product page costs you sales you'll never know about. Vital Lens lets you catch performance regressions the moment a new app or theme change lands.
- Spot LCP regressions after installing new apps
- Check CLS on collection and product pages
- Compare before/after a theme update
✍️
WordPress Bloggers & Site Owners
Plugin bloat is real. A new plugin can quietly destroy your LCP score. Vital Lens gives you real measurements as you browse, so you know immediately when something breaks your performance budget.
- Measure vitals after adding or removing plugins
- Check page speed across different post types
- Keep TTFB in check with hosting changes
🚀
Indie Hackers & Micro-SaaS Builders
You're moving fast. Performance often slips between deploys. Vital Lens is the lightweight layer that keeps you honest — no extra tooling, no accounts to manage, just accurate numbers on every page.
- Validate performance after every deploy
- Catch INP issues introduced by new JS
- Set budget alerts so nothing slips through
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Frontend Developers
You need real-field numbers, not just Lighthouse scores. Vital Lens captures actual runtime vitals as the browser renders the page — no synthetic environment, no guesswork.
- Inspect the exact LCP element and its selector
- Identify heavy resources by type and load time
- Test changes across different pages quickly
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Agencies & Consultants
Speed through performance reviews for multiple clients without switching between tools. Use History to show real measurements over time, and Compare to prove your changes made a difference.
- Baseline any site in seconds
- Show before/after proof of improvements
- Audit competitor sites during strategy sessions
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CMOs
You need fast answers, not dashboards. Echozat extensions give you on-demand page insights so you can make informed calls in reviews, pitches, and planning sessions.
- Spot SEO health of your web pages at a glance
- Measure your website's performance and identify optimization opportunities without leaving browser
- Get shareable reports without waiting on your team
What Users Say
Trusted by Builders Who Take Performance Seriously
From solo founders to dev teams — Vital Lens has become a daily part of the workflow for people who care about page speed.
★★★★★
"I used to only check performance when something felt slow. Now I open Vital Lens on every page I ship. It's changed how I think about frontend work — I catch things before users do."
★★★★★
"The Compare tab is what sold me. I installed a new payment app on my Shopify store and my LCP jumped by 800ms overnight. Vital Lens showed me exactly what changed before it hurt sales."
★★★★★
"We use this for every client audit now. Showing them real measurements on their own pages — not a simulated Lighthouse run — makes the performance conversation so much more concrete."
Real Results
What Faster Pages Do for Your Business
Founders and teams who catch and fix Core Web Vital issues consistently see meaningful improvements in organic rankings, conversion rates, and user satisfaction.
-62%
LCP reduction after fixing render-blocking resources identified via Resources tab
+18%
Conversion uplift following CLS fixes on a Shopify product page
5x
Faster performance review vs switching between tools and manual checks
0
Performance regressions shipped since setting up budget alerts
From the Blog
Go Deeper on Core Web Vitals
Practical guides for founders and developers who want to understand what the numbers mean — and what to actually do about them.
⚡
📦
Resource Optimization
How to Find and Remove the Scripts That Are Slowing Your Site Down
Using resource load data to identify which third-party scripts are hurting your INP and TTFB — and what to do instead.
Read Article →🛒
Shopify Performance
Core Web Vitals for Shopify Stores: A Founder's Field Guide
Why Shopify stores consistently struggle with LCP and CLS — and the practical fixes that don't require a developer.
Read Article →Common Questions
Frequently Asked
Is Vital Lens really free?
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Yes. Vital Lens is completely free to install and use. There are no paid tiers, no usage caps, and no features locked behind a subscription. Install it once and use it on as many sites as you need.
How is this different from running Lighthouse in DevTools?
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Lighthouse runs a simulated, throttled audit in a controlled environment. Vital Lens captures real runtime metrics as the browser actually loads the page — which reflects the real user experience much more accurately. It also tracks history automatically so you can see trends over time without running a test every time.
Does Vital Lens work on any website?
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Yes. Vital Lens analyzes whatever page is currently open in your browser — your own site, a client's, or a competitor's. As long as the page is publicly accessible, it will capture vitals automatically on load.
What does "Pin Baseline" do?
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Pinning a baseline saves the current set of vitals as a reference point for that page. The Compare tab then shows you how subsequent measurements differ from that baseline — making it easy to see whether a code change, a new plugin, or a server config update made things better or worse.
How do performance budget alerts work?
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In the Settings tab, you can define custom thresholds for LCP, CLS, INP, and FCP. If a page you visit exceeds any of those thresholds, Vital Lens flags it in the panel. You can also enable browser notifications to get an alert even when the extension popup isn't open.
Does the extension send my browsing data anywhere?
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No. Vital Lens processes everything locally in your browser. Page data and performance measurements are stored only on your device and are never sent to any external server. Your browsing activity stays private.
What's the difference between the popup and sidebar views?
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The popup view opens as a floating panel when you click the extension icon — great for a quick check. The sidebar view pins Vital Lens as a persistent panel alongside the page, so you can browse, scroll, and interact while keeping performance metrics visible the entire time.
Which browsers does Vital Lens support?
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Vital Lens is available as a Chrome extension and works on all Chromium-based browsers including Google Chrome, Microsoft Edge, and Brave.
Start Tracking Real Performance Today
Vital Lens installs in one click. From that moment on, you'll have Core Web Vitals on every page you visit — no setup, no account, no cost.
Add to Chrome — It's FreeAvailable on Chrome Web Store • No account required • Works on any site