One tool I will use every single time that I audit a website is GTMetrix.
I’ve seen comments about it, and that other speed testers like webpagetest.org provide “better data” and “more insights”, but GTMetrix does everything I want and helps me solve my problems.
As with every tool, you take its automated insights with a grain of salt. You leverage them, to guide further insight gathering, or to back up a specific decision.
GTMetrix gives me the data to pass on to dev teams, and help get issues patched.
Running a Speed Test with GTMetrix
It’s pretty simple to run a speed test in GTMetric.
- Enter the URL you’d like to test.
- Change the location you’d like the speed test run from. Highly recommend you get this as close to your audience as possible.
- (OPTIONAL) Change the browser you’d like to test from. This is where you can also select a mobile browser if you’d like to run a mobile speed test.
- (OPTIONAL) Select the speed if you’d like to throttle the speed test. Throttling can help show more “true to life” bottle necks, like with a poor mobile connection, but will also help smaller issues show up easier as everything will get exacerbated.
- (PRO REQUIRED) Ensure you have the video test flicked on, if you’re a pro user. You’ll get a bit more useful insight.
- Click Analyze, and run your website speed test.
How to interpret GTMetrix’s waterfall chart
The waterfall chart breaks down the exact points at when different resources are called, connected to, and downloaded.
Each resource is ordered based on when its loading starts.
All you have to ever really worry about here is when a specific resource is connected to, and when it finishes being downloaded. There are very few use cases you’ll run into as an SEO where anything in between is required.
Look through what items are being loaded and when, and then run through the standard checks from here to optimise.
Large files being loaded? Are specific requests taking too long? Too many files? External requests you didn’t know about?
Plenty of things to analyse here, but they’re very specific to each audit.
Each significant request stage is broken down by a coloured line. The following is what stage each of the coloured lines in the waterfall chart represent;
You can find some more info on the waterfall chart from GTMetrix directly, here.
Page Load Video by GTMetrix
One of my favourite features, particular to help better identify CLS issues,
Unfortunately, it’s a pro-only feature.
In saying that, it’s worth it to help out with these audits.
When running your original test, you can tick on video audit.
Or, when viewing an audit you can click ‘enable video and re-test’ and GTMetrix will re-run the test, including the video test this time.
Here’s an example video output, from the test I ran above of SammySEO.com
You can play/pause the video, or run it at 1x, 1/2x, or 1/4x speed.
Testing Core Web Vitals with GTMetrix
When you run a GTMetrix test, you get a basic overview of your core vitals.
You can extract a little more information from the waterfall chart, and a few other places in GTMetrix, but this overview can help you delve into each specific CWV separately.
So, if this isn’t the tool for you, what other options are there?
The top few that come to mind are;
- WebPageTest – https://www.webpagetest.org/
- Pingdom – https://www.pingdom.com/
- Google Pagespeed – https://pagespeed.web.dev/
Is GTMetrix pro worth it?
Yes, I believe GTMetrix pro is worth it. Well, for me anyway.
If you have an alternate speed tester you’re using, then it probably wouldn’t be.
Other tools have similar features, I have just used GTMetrix for years now, so have gotten used to it and understand what to look at a bit more than the other tools.