How to check site speed

Learning how to check your site speed doesn’t need to be daunting. This short guide will give you the basics, and point you in the right direction.

There’s no single metric

The first thing to understand is that there is no single metric or measurement for ‘speed’. There’s no simple number which you can use to measure how quickly your pages load.

Think about what happens when you load a website. There are lots of different stages and many different parts which can be measured. If the network connection is slow, but the images load quickly, how ‘fast’ is the site? What about the other way around?

Even if you try to simplify all of this to something like “the time it takes until it’s completely loaded“, it’s still tricky to give that a useful number.

For example, a page which takes longer to ‘finish loading’ may provide a functional ‘lightweight’ version while the full page is still downloading in the background. Is that ‘faster’ or ‘slower’ than a website which loads faster, but which I can’t use until it’s finished loading?

The answer is, “it depends”, and there are many different ways in which we can think about or measure ‘site speed’.

Understanding the loading process

From the moment when you click on a link (or hit ‘enter’ in your URL bar), a process begins to load the page you requested.

That process contains many steps, but they can be grouped into broad stages which looks something like this:

The “one second timeline” from Google’s site speed documentation

While Google’s documentation might be a bit ambitious about the timings of these stages, the model is helpful. Essentially, the process can be described as three stages of loading.

1. Network stuff

First up, the physical hardware of your device needs to connect to the Internet. Usually, that involves moving data through transatlantic fibre cables. That means that you’re limited by the speed of light, and how quickly your device can process information.

It’s hard to measure or impact this part of the process!

2. Server stuff

Here, your device asks your server for a page, and the server prepares and returns the response.

This section can get a bit technical, as it’s focused on the performance of server hardware, databases, and scripts. You may need to ask for help from your hosting provider or tech team.

We can measure the performance of the server with tools like NewRelic or DataDog, which monitors how your site behaves and responds from the ‘inside’.

They’ll provide charts and metrics around things like slow database queries and slow scripts. Armed with this information, you can get a better understanding if your hosting is up to scratch and if you need to make code changes to your theme/plugins/scripts.

The Query Monitor plugin for WordPress

WordPress has some great plugins for doing this kind of analysis, too – I’m a big fan of Query Monitor. This provides some great insight into which bits of WordPress might be slowing you down – whether it’s your themes, plugins, or environments.

3. Browser stuff

This stage is where the page needs to be constructed, laid out, colored in, and displayed. The way in which images load, in which JavaScript and CSS are processed, and every individual HTML tag on your page affects how quickly things load.

We can monitor some of this from the ‘outside-in’ with tools which scan the website and measure how it loads. We recommend using multiple tools, as they measure things differently, and are useful for different assessments. For example:

  • WebPageTest is great for providing a ‘waterfall’ view of the website, and how all of the assets load.
  • Google PageSpeed Insights is a bit simplistic, but it provides ‘real user metrics’ of your website, straight from Google.
  • Lighthouse for Chrome provides an incredibly sophisticated analysis of the performance and behavior of the site, but it can be hard to digest!
  • Chrome Developer Console shows you exactly what’s happening as your site loads, on your computer, in your browser.
  • Speed report in Google Search Console shows you how fast or slow your pages load over any given time.
WebPageTest results for

These kinds of tools are great for spotting things like images which need to be optimized, where your CSS or JavaScript is slow, or where you’re waiting for assets to load from other domains.

Universal metrics

Despite all of these moving parts, there are a few universal metrics which make sense for all sites to measure, and optimize for. These are:

  • Time until first byte, which is how long it takes until the server responds with some information. Even if your front-end is blazing fast, this will hold you up. Measure with Query Monitor or NewRelic.
  • Time until first contentful (and meaningful) paint, which is how long it takes for key visual content (e.g., a hero image or a page heading) to appear on the screen. Measure with Lighthouse for Chrome.
  • Time until interactive, which is how long it takes for the experience to be visible, and react to my input. Measure with Lighthouse for Chrome.

These are much more sophisticated metrics than “how long did it take to load”, and, perhaps more importantly, have a user-centric focus. Improving these metrics should correlate directly with user satisfaction, which is super-important for SEO.

A Lighthouse report for showing key metrics

You can read more about these metrics in Google’s documentation.

Wrapping this into a process

  1. Use an ‘outside-in’ tool, like WebPageTest to generate a waterfall diagram of how the website loads.
  2. Identify bottlenecks with servers and the back end. Look for slow connection times, slow SSL handshakes, and slow DNS lookups. Use a plugin like Query Monitor, or a service like NewRelic to diagnose what’s holding things up. Make server, hardware, software and script changes.
  3. Identify bottlenecks with the front end. Look for slow loading and processing times on images, scripts and stylesheets. Use a tool like Google PageSpeed Insights or Lighthouse for Chrome for suggestions on how to streamline how the page loads.
  4. Use Lighthouse for Chrome to measure your key metrics, like time until first meaningful paint and time until interactive.

Have we missed anything? Let us know in the comments!

Read more: Improving site speed: Tools and suggestions »

Coming up next!

17 Responses to How to check site speed

  1. Sneha
    Sneha  • 4 years ago

    Thanks..Google PageSpeed Insights worked for me..

  2. Najot
    Najot  • 4 years ago

    Page/Site speed is much important part of testing any website. If a site’s processing speed is low then it can become the reason of your high bounce rate, moreover, a user does not expect to wait much more than 4-5 seconds on an average.

  3. Mary
    Mary  • 4 years ago

    Those may tell you what is wrong, but It doe nothing to tell you what is causing the problem or how to fix it.

  4. Dave Hoe
    Dave Hoe  • 4 years ago

    Really helpful post. Pingdom tools is also good for a holistic view of page load times

  5. suresh dorge
    suresh dorge  • 4 years ago

    Nice Information, I like your article. but I have a question though. how can increase my website speed especially for mobile devices?
    If in case, Amp is the only option then how can I do that?

  6. color splash
    color splash  • 4 years ago

    thanks for sharing this article.this help me a lot for testing my website speed and improving it .

  7. Manjula Fernando
    Manjula Fernando  • 4 years ago

    This is life saving information! Please do a Review on Hosting sites as well!

  8. jeroen
    jeroen  • 4 years ago

    Hi Jono,

    if you have a kpi for TTFB, FMP FTI, what would it be?


  9. Wrocław
    Wrocław  • 4 years ago

    unfortunately my site has got not very good page speed, i need to contact with my webmaster :(

  10. Antonio
    Antonio  • 4 years ago

    Thanks, For sharing this article. it mean alot and provide valuable information. My page speed is like 20 25. After reading it and using this technique. It cross the 70, I know i need to work in it to boos it up. But it drastically boost my page speed. Thanks! Yoast

  11. Freethinker
    Freethinker  • 4 years ago

    Google PageSpeed now powered by LightHouse. What is the difference with LightHouse Chrome addons?

    • Jono Alderson

      Have a play! The reports are a bit deeper, and there are some nifty configuration options.

  12. Toby
    Toby  • 4 years ago

    I was always testing the websites speed test with Pingdom tools & GTmetrics while I think that a tool like Newrelic is much much better.

    Is there any way/tool to check whick javascript slows down the website and make the browser to use a lot of CPU?

    Thanks for the article!


    • Jono Alderson

      I’d be careful to rely overly on one tool – NewRelic isn’t necessarily *better*, but rather, *different*. It has a focus on the back end, which might not be where all of your issues are. In fact, you might find that the biggest issues you have are with things which NewRelic doesn’t measure, like, e.g., how CSS is served by your website. I’d find a healthy mix of tools, and use them all to find opportunities!

      When it comes to JS and CPU performance, Lighthouse is a good place to start – but if you want to get really deep, you can wade through some of the advanced settings in the Chrome Developer Console!

  13. ginzlucena
    ginzlucena  • 4 years ago

    Thank you for this article. I will check my site loading.

  14. Bill
    Bill  • 4 years ago

    Great article, and your plugin is not bad, but I would like to suggest a few things.

    1. Do not limit the size of the Description, even in the free version.

    2. It would be nice if the number of keywords can be added more.

    3. Expand the functions of the free version, and you will have more users.

    Good luck, guys

  15. Surya Shrivastava
    Surya Shrivastava  • 4 years ago

    Since I am facing website loading (speed) issue for my site. After reading your article I would like to say I could be overcome of my problem by using such fantastic tools.

    Specially I would like to user “Query Monitor” Plugin for WP site.

    Thanks again for sharing such wonderful techniques with us.

    Best Regards,