If you're trying to optimize your site's speed, then you should be using a performance assessment tool such as Google PageSpeed Insights or GTMetrix. Wondering which one you should trust to measure your site speed?
There's no easy answer, since they both have their strengths and weaknesses, and you should actually use them both. In this article, we'll go over the pros and cons, and explain when you should pay attention to the report from each of the tools.
Google's PageSpeed Insights is an essential tool if you're trying to optimize your site's speed. While the other tools report some useful information that PageSpeed Insights doesn't, you should always check your site with this online tool.
One thing PageSpeed Insights has that other tools lack is the field data section. Google collects data on page load times from Google Chrome users, and reports it within PageSpeed Insights. This is the same data that Google uses for its Core Web Vitals, which you can also find in Google Search Console. Page speed is a direct ranking factor with Core Web Vitals, and with this field data, you can get an accurate representation of how Google sees your site's speed.
By default, you'll see mobile results in Google PageSpeed Insights. With over 50% of mobile traffic now coming from mobile devices, it's critical that you page is well optimized for mobile. With PageSpeed Insights, you'll see lab results for a simulated mobile device on a slow 4G connection.
Although internet speeds in general have been increasing, it's still common that mobile users will find themselves on a slow connection at times. You should aim to have your pages load quickly in situations like this, and PageSpeed Insights makes it easier to test for the near worst case.
If you look into the "opportunities" section, then you'll see PageSpeed Insights gives diagnostics for what is slowing down your page, so have actionable insights when optimizing for speed. Although it can be confusing to know how to fix these errors, our blog has free resources to explain what they mean. We also have a step-by-step course to walk you though setting up your website for optimal speed.
Google PageSpeed Insights is a great tool, but when compared to other tools like GTMetrix, it's not without its downsides. That doesn't mean you shouldn't use it, just that you should know when to check other tools instead.
Sometimes PageSpeed Insights can have overly harsh results with its lab data for certain sites, when if you look at field data, the results are actually not so bad. For example, take a look at the PageSpeed Insights results for a Shopify store like LTTStore.com. You'll see the lab results look quite bad, but based on actual user data in the field report, it's reasonably fast.
There are some important metrics that you won't see in PageSpeed Insights, such as TTFB (time to first byte). PageSpeed Insights will tell you to reduce server response time if that time is outrageously long, but it sets the bar quite low, and using GTMetrix you can always see the true value.
GTMetrix is great for the extra data you get back when compared to PageSpeed Insights. Its performance test reports things you won't see in PageSpeed Insights.
One of the most useful parts of GTMetrix is the waterfall analysis. You can view a chart of the order and timings for each resource that your page loads. This is useful for determining which resources are slowing your page down the most, and which ones don't need to be loaded at all.
GTMetrix offers some useful metrics that you don't need with Google PageSpeed Insights, like TTFB and onload time. If you want to get a full picture of your site's performance, you'll want to test in both of these tools.
With a free account, you'll remove the default limits on how many tests you can run per hour. You'll also unlock the options for test locations and internet connection speed. GTMetrix can also test with adblock on or off, and create a video of your page load so you can see exactly how it looks through the load process.
GTMetrix reports some different metrics you don't get with PageSpeed Insights, however, it's not better in all ways.
One major downside to GTMetrix is that the score is overly optimistic. By default, it tests with the desktop version of Chrome on a faster connection, and can report a good grade for sites that really pretty slow. You'll need a pro account to unlock mobile devices, browsers, and every test server.
You should be optimizing for the worst case, a smartphone on a slow mobile connection. Although desktop and mobile are both important, speed on desktop comes easily once you've got good speed on mobile.
There's lots of other page speed testing tools that you can run to get a better idea of how your site performs. Here are some of the best and most popular ones.
Pingdom Tools is a testing tool that offers similar recommendations and metrics to PageSpeed Insights. It's great for a quick overview of your site's performance, but doesn't tell which resources specifically are slowing the site down.
While you can change your test location to various different options, something that not all tools offer, this tool doesn't provide as complete of results when compared to GTMetrix and PageSpeed Insights.
Google Lighthouse is a page speed testing tool built into Google Chrome. Additionally, it includes audits for SEO, usability, best practices, and progressive web app standards. You can use the tool from Google Chrome's developer tools from the Lighthouse tab.
The methods for testing performance in Lighthouse are same as Google PageSpeed Insights lab tests, but it's a good idea to test with this tool as well. You should try to fix any warnings not just in the performance section, but the other sections as well.
You should use a variety of different testing tools when optimizing and measuring your site's performance. It depends on what you're testing for.
For a general overview of your site's performance with some specific actionable insights, PageSpeed Insights is one of the best tools to use. Its throttled mobile tests give a more stringent, yet more accurate view of how your site will load in less than ideal conditions.
GTMetrix is easier to please when it comes to overall speed score, but offers some important information that PageSpeed Insights doesn't. The additional metrics like TTFB are very helpful when setting up caching or a CDN. Its waterfall analysis is great for determining which resources are being loaded, and which are hurting your performance.
It's good to also use Google Lighthouse for the additional audits, even if you've perfected the speed scores in GTMetrix and Google PageSpeed Insights. While the performance metrics look the same as PageSpeed Insights, you can identify some additional issues by using more tools.
We hope this article was helpful with understanding the differences, strengths, and weaknesses of the most popular speed tools. When comparing PageSpeed Insights vs other tools like GTMetrix, it's important to know when to use which tool.
To identify speed related issues is only half the battle. If you're looking for how to fix the issues you've discovered after performance testing, then our blog has the information you need to understand these errors, and where to start with fixing them as you work
to improve load time.
We also offer a video course that walks you through setting your site up for optimal speed, step by step. At Fastify, our goal is to give online business better results through speed optimization.