How should I measure my speed?

Website speed is very complex because it is affected by so many factors. Each of your customers will experience the speed of your site in a different way.

As a result, there is no single metric that allows you to accurately measure your speed.

Understanding the different types of speed-related metrics and evaluating them all together is the best strategy.

PageSpeed Scores

PageSpeed scores generated by Google’s PageSpeed Insights are a very popular way to measure shop speed.

The scores are calculated based on how closely your site follows various development best practices related to site speed.

Pros:

• Presents a detailed list of potential speed opportunities
• Provides insights into Google’s standards 

Cons:

• Highly inconsistent scores (can vary by up to 20 points)
• Scores don’t necessarily correlate with real-world speed
• Heavy focus on Google’s priorities for the web

Conclusion:

Be cautious when evaluating your speed based solely on these scores.

If you’re just getting started with speed, your PageSpeed scores can be insightful.

The list of opportunities provided can be a great starting point to understand what types of improvements would be most impactful for your site’s speed.

Unfortunately, the variance in PageSpeed scores makes them a very unreliable way to judge the effectiveness of various speed improvements.

Additionally, the fact that PageSpeed scores are calculated based on compliance with development best practices, rather than an evaluation of real-world speed can be deceptive.

Load Time

Load time can be calculated using several different methods. The two most common are ‘on load’ and ‘fully loaded’.

Plug in Speed calculates your ‘on load’ loading time. This is the time it takes before a customer can fully view your page. Customers will usually see all of the content and images on the page at this point.

Making this portion load as quickly as possible is important for your conversion rate.

Another loading time measurement is called ‘fully loaded’. This is the time taken for everything on the page to load, including things the customer doesn't see, like tracking and widgets like the Facebook like button.

This fully loaded loading time does not impact conversions or SEO.

There are other, more specialised metrics available, such as first contentful paint and time to interactive.

Pros:

• Understand the experience of your customers

Cons:

• Is measured in many different ways
• Can vary each time it is measured

Conclusion:

Load time is a very helpful metric to understand how your customers experience your shop.  

Since load time can be measured in several ways it is important to understand how your load time is being calculated.

Load time measurements will vary depending on many factors. Load times generated through one tool should not be compared to load times generated from another.

It is also best to use an average rather than a single measurement.

Image and Code File Size

Each time a customer views a page on your shop various image and code files need to be loaded.

Larger files are slower to load. Reducing the size of these files will allow them to load more quickly.

File sizes can be measured before and after size-based speed fixes to evaluate the significance of the speed fix.

Pros:

• Is an objective metric
• Can be used as a strong benchmark for speed improvements

Cons:

• Used alone, does not provide insight into the customer experience
• Only measures size-based speed fixes

Conclusion:

This provides the most objective metric for evaluating the effectiveness of size-based speed fixes.

Does not provide any insight into the impact of types of speed fixes.

You can read more about the difference here: How do speed fixes work?

Should be used along with an average load time metric to provide the best insight into the actual customer experience on your shop.

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