A website's speed determines whether a visitor stays in the first few seconds. Pages that load slowly, shift content while loading or respond late to taps lose both the user and the conversion. Google evaluates this experience with metrics called Core Web Vitals, and Lighthouse is the most widely used tool for testing that performance.
In this guide we cover what the Core Web Vitals metrics mean, how to read a Lighthouse score, the most common performance problems and a 5-step plan to speed up your site.
What are Core Web Vitals?
Core Web Vitals measure real users' page experience from three angles:
| Metric | What does it measure? | Good value |
|---|---|---|
| LCP (Largest Contentful Paint) | How long it takes for the main content to appear | 2.5 seconds or less |
| INP (Interaction to Next Paint) | How quickly clicks and taps get a response | 200 milliseconds or less |
| CLS (Cumulative Layout Shift) | How much content shifts while the page loads | 0.1 or less |
These values can be tracked with real user data in the Core Web Vitals report in Google Search Console.
How to read a Lighthouse score
Lighthouse loads the page in a controlled test environment and scores performance from 0 to 100. The score is calculated from measurements such as when the first content appears, when the largest content appears, how long the main thread is blocked, layout shift and how quickly the page becomes visually complete.
Lab data vs real user data
Lighthouse is a lab test; it measures a single device and connection scenario. Field data in Search Console and PageSpeed Insights reflects the experience of real visitors. The two should be evaluated together, with priority given to real user data when making decisions.
The most common performance problems
- Unoptimised images: Oversized images in older formats without declared dimensions.
- Heavy JavaScript: Unused libraries, unnecessary plugins and code that blocks the page.
- Third-party scripts: Uncontrolled loading of analytics, chat, advertising and social media code.
- Font loading: Fonts that load late, leaving text invisible or causing it to shift.
- Slow server response: Missing caching and insufficient hosting.
5 steps to speed up your site
- Measure the current state: Record Lighthouse and Search Console data for mobile and desktop.
- Optimise images: Use modern formats such as WebP, correct dimensions and lazy loading for off-screen images.
- Reduce JavaScript: Remove unused code and defer non-critical scripts.
- Audit third-party code: Keep only what is truly needed; load analytics and marketing code after consent.
- Improve server and caching: Use page and file caching, compression and a content delivery network.
Staying fast with animation and video
Hero videos and animations create an impressive experience, but they reduce performance if not built correctly. Loading the video after the main content, showing a static image on the first frame and animating only lightweight properties such as transform and opacity is the way to deliver visual impact without lowering the score.
Fast, measurable websites with All Inn Agency
All Inn Agency's web and e-commerce service builds fast, measurable websites with Core Web Vitals targets set from the start, and runs performance audits and improvements for existing sites. We handle the technical SEO side together with our digital brand and SEO work.
If you are planning a new site, see our corporate website checklist. Let's review your site's performance together: talk to the assistant on our homepage or reach us through the contact page.
Frequently asked questions
No. Google considers page experience in rankings, but content quality and relevance matter far more. A fast site, however, directly improves user experience and conversion.
The Lighthouse mobile test simulates a slower processor and connection. As a result, the mobile score is usually lower and improvements should prioritise mobile.
Network and server conditions change from test to test. Looking at the average of several measurements and tracking real user data gives more reliable results.
Yes. If the video loads after the main content, a static image is shown on the first frame and animations use lightweight properties, a high score can be maintained.
It is possible, but themes with many plugins and bundled code need more optimisation. A clean, lightweight theme is a significant advantage.
After every significant change and at least once a month. The Core Web Vitals report in Search Console is a good starting point for regular tracking.
Move your workflow forward with a measurable goal
Let's clarify which process you want to improve together. From needs analysis to a delivery plan — let's talk through the roadmap.