How to Use GTmetrix to Improve Website Speed and Core Web Vitals

Hey friends! Eli here 👋 — solopreneur, automation nerd, and your go-to guy for cutting through the noise in the world of SaaS, SEO, and AI tools. I test a LOT of products so you don’t have to waste time on fluff. Today, we’re digging into a tool I personally rely on for boosting my own sites and my clients’ SEO performance: GTmetrix.

If your site feels slow, you don’t know why your Core Web Vitals are tanking, or you want concrete, pro-level methods for faster load times, keep reading. We’ll walk step-by-step through how to use GTmetrix to speed up your site and rank better on Google.

And yeah—I’ll also drop some pro-level tips that most guides skip. Let’s go 🚀

What is GTmetrix (and Why You Should Care)

GTmetrix is a free (with optional paid tiers) performance testing and monitoring tool powered by Google Lighthouse, enhanced with data from Chrome UX reports. In plain English? It shows you:

✅ What’s slowing down your site
✅ How Google sees your site’s performance
✅ Specific changes you can make today

If you’re serious about SEO, conversion rates, and user experience, this tool is non-negotiable. Start using GTmetrix here →

How to Run Your First GTmetrix Test (Step-by-Step)

Ready to get started? Here’s how to run your first speed test:

1. Go to GTmetrix.com

No install required. Just paste your URL into the test bar on the homepage.

2. Create a Free Account (Optional but Smart)

Creating an account lets you:

Choose test server locations
Simulate different devices or throttled speeds (mobile, 3G)
Save reports for comparison

Creating a free GTmetrix account takes 90 seconds and gives crazy value for $0.

3. Input Your URL

Test your homepage first. Then, test critical pages like landing pages or checkout flows.

4. Choose Analysis Settings

Click “Analysis Options” (only visible when you’re logged in):

Test from a location close to your site’s audience (e.g. US East for most North American traffic)
Simulate mobile browsing if your audience is mobile-heavy
Throttle speed if you want to simulate real-world slower connections

Then click “Test your site.”

Boom—GTmetrix gets to work. You’ll get a full performance report within seconds.

When your results load, the first thing you’ll see is your GTmetrix Grade:

A letter grade (A–F) based on performance and structure
Below that, your Web Vitals:
- LCP (Largest Contentful Paint) — should be under 2.5s
- TBT (Total Blocking Time) — under 200ms
- CLS (Cumulative Layout Shift) — under 0.1

These are literally Google ranking signals now. Lower scores = lower rankings. 😬
So if GTmetrix shows poor LCP or TBT, Google probably is too.

Every action from here targets one of these Core Web Vitals.

👉 Want to improve your vitals today? Run your site through GTmetrix now →

How to Read the GTmetrix Waterfall Chart Like a Pro

Now this part looks geeky — but once you get the hang of it, you’ll feel like a wizard.

What is the Waterfall Chart?

It’s a beautiful timeline that breaks down exactly how each file (JS, CSS, images, fonts, etc.) loads on your site.

What to Look For:

Long bars — these are your slow files
Red or yellow warnings — bad DNS, connection, or long blocking times
3rd-party scripts — like analytics, social media, or marketing widgets that slow you down

Click any file to see:

Load time
Wait time
Size
Initiator (what called it?)

🧠 Pro Tip: If you see things like Facebook pixels or YouTube iframes near the top of the chart slowing your site—consider lazy loading or deferring them.

Want a live look at your waterfall chart?

Run a Speed Test on GTmetrix

Best GTmetrix Settings for Page Speed Optimization

Here’s how I customize GTmetrix for every test:

Location: Closest to where your audience lives
Device: Desktop or Mobile (use mobile if your site is responsive-heavy)
Connection: Throttle to 3G or 4G LTE to simulate mobile users
Ad Block Option: Turn ON to see how ads affect performance
Video Option for PRO Users: Record load in real-time to catch jank

Want to monitor speed over time with advanced features?

Upgrade to GTmetrix PRO

GTmetrix Pro Tips (From Years of Real-World Use)

These are the tips I give my web dev clients and digital marketers:

Track Changes Over Time: Make a tweak, run a new test. Compare reports.
Test Individual Pages: Don’t just test your homepage. Test product pages, blog posts, contact forms.
Use Annotations in Paid Plan: Label big updates like new plugins or CDN switches.
Combine With Other Tools: Use GTmetrix to FIND the problem, then tools like WP Rocket or LiteSpeed Cache to FIX it.

Common Optimization Mistakes to Avoid

Even smart devs fall into these traps:

😵 Testing only once — Load times fluctuate! Run 3–5 tests for realism.
🧩 Ignoring mobile — Mobile UX now dominates overall web traffic.
🎯 Focusing on grades, not vitals — A shiny “A” means nothing if your LCP is slow.
🎞️ Not compressing media — PNGs, self-hosted videos, uncompressed logos = fail.

[Bonus] Best WordPress Setups for GTmetrix Wins

Running WordPress? These combos consistently pass GTmetrix and Core Web Vitals:

Theme: Astra, GeneratePress, or Kadence (super lightweight)
Caching Plugin: WP Rocket + Autoptimize or Perfmatters
Hosting: LiteSpeed, Cloudways, or Kinsta
Image Optimization: ShortPixel or Imagify

And yes—these work because I use them on my own client sites.

🔥 You can track those improvements and hold clients accountable using GTmetrix!

Start Testing With GTmetrix

GTmetrix FAQ (SEO Goldmine)

Q: Is GTmetrix free to use?
A: Yes! The free plan gives detailed analysis, waterfall charts, and Lighthouse-powered reporting. Pro plans unlock monitoring, advanced settings, and video recording.

Q: Is GTmetrix better than Google PageSpeed Insights?
A: GTmetrix adds more visual analysis (like the waterfall), test location options, and saves historical data. For in-depth diagnostics, it’s the better tool.

Q: Will GTmetrix help me pass Core Web Vitals?
A: Absolutely — it shows you exactly which metrics are underperforming and what assets (like fonts, scripts, or images) are causing it.

Q: How often should I run tests?
A: Regularly — especially after adding plugins, changing themes, or deploying updates. Pro plan users can even run automatic hourly tests.

Final Thoughts: Your Next Move Matters

You’ve just learned how to:

✔️ Run a site speed test
✔️ Analyze your Core Web Vitals
✔️ Interpret GTmetrix’s waterfall chart
✔️ Tweak your page to load faster
✔️ Avoid optimization mistakes

If I could give one last piece of advice?

🎯 Don’t just chase perfect scores. Use GTmetrix to understand your performance, and then optimize for your users—not just Google.

Want faster page loads, happier visitors, and higher Google rankings?

Test Your Site on GTmetrix Now

I’ll catch you in the next deep dive! Until then, keep building smarter—not harder.
— Eli 💡 @NextGenAIFinder